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Re: Biology Q&A archive/Bio FAQ
« Reply #15 on: April 30, 2018, 09:05:52 pm »
U4 AOS 1 Human change over time
Relevant study design dot point
• shared characteristics that define primates, hominoids and hominins

• major trends in hominin evolution from the genus Australopithecus to the genus Homo including structural, functional and cognitive changes and the consequences for cultural evolution

• the human fossil record as an example of a classification scheme that is open to interpretations that are contested, refined or replaced when new evidence challenges them or when a new model has greater explanatory power, including whether Homo sapiens and Homo neanderthalensis interbred and the placement of the Denisovans into the Homo evolutionary tree.

What are the major trends from genus Australopithecus to genus homo?
Also what are major trends from genus Australopithecus to genus homo

I've got the habilis tool makers, erectus walking upright and using fire but I don't know what else to add?
Fora Magnumen (Idk how to spell it) moves central - allows for bipedalism
Shorter arm-to-leg ration - allows for bipedalism
Bipedalism allows us to free up our hands to use tools
Leads to larger brain sizes needed to use these tools
Larger brain also leads to development of primitive culture
What is the significance of the foramen magnum and wider pelvis in humans?
what is the significance of the foramen magnum and wider pelvis in homo sapiens?
The foramen magnum position in Homo sapiens allows for the spinal cord to be placed along our backs... which in turn lets us to stand upright on two feet. Secondly the wider pelvic outlet in Homo sapiens is an adaptation permitting the birth of offspring.
Just to add to that significance: While hominid family always had a pelvic outlet to allow reproduction + birth of offspring, the key significance here is the wider pelvic outlet in homo sapiens that allows for offspring with a larger head (which is limited evolutionarily by size of opening) and hence the evolution of larger brain size which can correspond to increasing intelligence that characterizes our genus.
What is a hominoid?
I'm just finishing off my notes for the course - down to hominin evolution.

Can someone please explain to me exactly what a hominoid is? I'm still confused! Specifically characteristics of hominoids for the point on the study design about "shared characteristics which define primates, hominoids, and hominins".

Thanks in advance  :)
Hominoids are humans, the great apes and all their ancestors. They have relatively big brain capacity, long gestation period, opposable thumbs/big toes and depth vision.
What are some evolutionary trends from Australopithecus to Homo?
Hey everyone, I'm struggling a bit with the trends in evolution from Australopithecus to Homo Sapiens, can anyone give me some bullet points on the general trends?
Also, what feature define Hominoids?

Thanks in advance
Decreased eye ridge
Increased brain case
Face becomes less sloped
Spine becomes S shaped
More central Foramum Magnum
Pelvis is more narrow
What’s the difference between a hominid and a hominin?
main difference between between hominid and hominin? thanks :)]
As far as I know:
Hominid - all modern and extinct great apes - gorillas, chimpanzees, orangutans and humans, etc. but not gibbons
Hominin  - all humans & extinct human ancestors (basically a branch of hominids)
What are some traits that indicate an individual was bipedal?
1)bipedal ism is simply the ability to walk on two (hind) legs. correct?
2) 'what feature would enable an observer to conclude the individual was bipedal' - i was going to talk about cranial capacity etc. is this on the right tangent? thanks :)
In regards to question 2, from what I understand these are some things you can dicuss:
- position of the foramen magnum
- valgus angle
- pelvis structure (shorter and broader)
- length of lower limbs (longer in bipedals)
- spine curvature
- structure of ribcage
How does the higher variation in African mtDNA support the out-of-Africa theory?
How does having higher MtDNA variation in Africa support the out-of-Africa theory?
My understanding is that:
-Highest mtDNA variation would expected to be found in the place in which homo sapiens have been living longest, due to more time to allow for genetic mutations to occur and be passed on.
-Also, when migrating out of Africa, only small populations would have migrated out. This would result in large European populations being formed from only a few founders with limited genetic variability, making the mtDNA variance in non African populations lower due to the founder effect.
What is meant by gene flow occurring between Neanderthals and humans?
2) When they say gene flow occurred between Homo neanderthalensis and Homo sapiens, do they mean there was movement of new alleles for existing  traits or completely new genes encoding for entirely new traits?
2) Gene flow is the movement of alleles between populations. It does not involve new alleles, only mutations can create new alleles. Gene flow between neanderthals and humans is referring to interbreeding, producing offspring that have some human and some neanderthal DNA (which would make them the same species, which they're not so it's a bit confusing - people aren't really sure). This neanderthal DNA is now present in the human population (ie. it is represented in their gene pool and can be passed down through generations. This is what they mean by gene flow - The alleles moved from the neanderthal gene pool to the human gene pool and are now 'available' for the next generation. - Tell me if this doesn't make sense and I'll try and explain it a different way.
What is an example of a functional change from Australopithecus to Homo?
Regarding this study design dot point:

"major trends in hominin evolution from the genus Australopithecus to the genus Homo including structural, functional and cognitive changes and the consequences for cultural evolution"

What are examples of "functional change"? Again, can't find this information anywhere!
Good evening,
I'm not sure if I'm completely right about this one, but structural evolution typically refers to any change in the morphology of the body over time (without considering its implications and consequences). Functional trends would probably be things like the precision grip, bipedalism, having a wide ribcage to compensate for a diet with high fibrous matter, all the implications of structural, cognitive and cultural evolution (to a lesser extent). Hope that cleared some confusion. :)
What do we need to know about hominin evolutionary trends?
Hey guys,

  • Major trends in hominin evolution from the genus Australopithecus to the genus Homo including structural,
    functional and cognitive changes and the consequences for cultural evolution
With regards to this dot point, do we need to learn about the pre-human hominins (Australopithecines, Paranthropus, and Ardipithecus) What specifically do we need to know?

Also, which species of the Homo genus should we learn and how much do we need to know?
Am I missing anything from this list: Homo habilis, Homo erectus, Homo floresiensis, Homo heidelbergensis, Homo neanderthalensis.

I think you just need to be able to identify if a species belongs to a particular genus (see Q7 on the 2017 exam) and you need to know general trends that occurred from Austra. to homo. and where para. and ardi. fit along that timeline.

I don't really know how much you need to learn about each of the H. species, but you should be fine so long as you can differentiate between them, know where each fits on the timeline, and know what evolved into humans, and what coexisted with us. <-- This could be too much info, but I don't think you'll need more than that.
What is the evolutionary purpose of the angles our bones are at?
What was the purpose of the angled arrangement of the femur relative to the tibia, and the purpose of bowl-shaped pelvis and short hipbone?
I'm trying to better understand why they were developed.
they are all anatomical adaptations which have allowed bipedalism in the homo genus.
What are hominids, hominins, and hominoids?
What does it mean by hominid, hominin and hominoid?
They're different classifications. Hominin is the most specific. All hominins are hominids and all hominids are hominoids.

Hominoids: Great apes, lesser apes.
Hominids: Great apes
Hominins: Modern humans and our extinct bipedal ancestors.
What are hominoids/Hominidae/homininae/hominini?

Is someone able to tell me what the members of the following:
Hominoidea (hominoids)
Hominidae (hominid)

Also, is it Homininae or Hominini that is referred to as hominin, and what is the other referred to as?
The Homonoids are members of superfamily hominoidea, composed of apes which are mainly distinguished from other primates by their lack of a tail, tendancies towards erectness, 5 cusped dentition and a relatively large brain.

The Homonids are members of family hominidae, composed of the great apes and typically have a more complex social behaviour. This includes orangutans in addion to those of the hominines.

The subfamily Homininae (the hominines) a characterized by ground dwelling and a larger cerebral cortex. These include gorillas, chimps and ourselves.

The tribe hominini (the hominins) are primarily defined by bipedalism and the morphological characteristics that support such (more central foramen magnum, large heel bone, 'S'-shaped spine. There is no consensus on whether the subtribe panini (chimps) belongs in this tribe or in its own. I think for the purpose of our course we consider it not included. If not, perhaps someone can correct me otherwise.
Biological and cultural evolution (timeline)

And when asked for a timeline for biological evolution, should this be the changes seen as species evolve (e.g. species X evolves x trait at year x), or the time at which the change occurred? As for cultural evolution, what should I be focusing on as key changes?

Thanks! :D
I think with reguards to biological evolution, you want to be talking about the evolution of different life forms (ie. first simple single celled life, first eukaryotic life forms, first plants...)

Personally I don't think you should worry too much about cultural evolution. I think you should know what it is and understand a couple of examples, thats all.

Hopefully this helped!
What is cultural evolution and what are its consequences?
-  major trends in hominin evolution from the genus Australopithecus to the genus Homo including structural,
functional and cognitive changes and the consequences for cultural evolution. I missed the class where we discussed this dotpoint and my teacher only provided me with the structural changes, but what are the functional and cognitive changes? and what exactly is cultural evolution and it's consequences?

Thanks so much!!
I'm not really sure on functional changes - I didn't really understand this back when I originally learnt about it.
Cognitive changes will just be referring to increased intelligence.
Cultural evolution is just the passing down of knowledge, rather than each individual having to learn for itself it can be taught things, therefore that individual has time to learn completely new things which it can then pass down, rather than just learning the same things its parents did and then dying. Over time this results in lots and lots of accumulated knowledge.

I think what this dot point is getting at is that structural evolution (increased cranium capacity) allowed for bigger brains (potentially this is functional change??) which made them smarter (cognitive change) which allowed them to learn and teach others (cultural evolution)
How will the human fossil record be assessed in an exam?
•    the human fossil record as an example of a classification scheme that is open to interpretations that are
contested, refined or replaced when new evidence challenges them or when a new model has greater
explanatory power, including whether Homo sapiens and Homo neanderthalensis interbred and the placement
of the Denisovans into the Homo evolutionary tree. For this one, I was wondering how they would assess this in an exam and what I need to gather from this dotpoint
I think all you'd need to know for this would be about why the human fossil record is incomplete (fossilisation being rare, finding fossils being rare etc.), the theories for the evolution of humans, and evidence that suggests that denisovans interbred (DNA being found in some modern human populations). On our exam last year we got a question about Denisovans, I can't remember what it was about exactly but it might be worth having a look at it.
Why are H. neanderthalensis and H. erectus considered separate species if they interbred?
How can Homo Neanderthalensis and Homo Erectus interbreed if they are separate species? Is this an exception to the rule...
There’s lots of exceptions to our definition of a species. For example, how do you define a species if it reproduces asexually? Some people use exceptions like if it’s only males of one species and females of the other that can interbreed (and not vice versa) then they’re seperate species, but until there’s a better definition of what a species is, just accept that they are seperate despite them not fitting the definition.
I'm not 100% sure which "species" could interbreed but the "strict" definition for a species we take in VCE biology is that if two organisms can interbreed and produce a fertile, viable offspring they are the same species. Plenty of different species (e.g. lion and tiger) can interbreed and produce offspring (Liger, Tigon) but the offspring are not fertile.

But it's important to know that these are the arbitrary rules we have chosen to define a species so taking a strict definition may mean they are the same species. (VCAA 2015 Question 10 discusses this a bit for H. sapiens and H. neanderthalensis).
What are "prominent heelbones" and how do they provide a selection advantage?
5. What are "prominent heelbones" and how do they provide a selection advantage?
5. Prominent heelbones refers to your heel sticking out. Like if you point your toes you have a bump where your heel is. The selection advantage is that they make bipedalism more efficient and does a better job of supporting the increased weight associated with bipedalism & evolution.
Why is an ‘S’ shaped spine important?
5. Why s-shaped spine is important? acts as a spring to facilitate bipedalism.
5. Yeah. Probably should include something about it making bipedalism more efficient

U4 AOS 2 DNA manipulation
Relevant study design dot points
• the use of enzymes including endonucleases (restriction enzymes), ligases and polymerases

• amplification of DNA using the polymerase chain reaction

• the use of gel electrophoresis in sorting DNA fragments, including interpretation of gel runs

• the use of recombinant plasmids as vectors to transform bacterial cells.

When is PCR used?
Describe 3 situations where only very small DNA samples may be available for sampling and PCR can be used
-  In crime scene investigations. Availability of small samples of blood; to get a DNA fingerprint of the person whose blood it is.
   This may also include semen investigation for a rape victim (people generally hear crime and think blood.)
-  Archaeological and/or paleontological investigations.
-  Paternity testing.
What temperatures are needed for PCR?
What temperature is a PCR mix raised to? There are several degrees so does anyone have a definite? Thanks.
I would say 95 degrees for denaturing, 55 degrees for extending, and 72 degrees for extension.
Why do we need sticky ends rather than blunt ends to insert genes?
What would be the advantage of restriction enzymes producing sticky ends in recombinant DNA technology than blunt ends?
Blunt ends are quite useless, if you have sticky end, you have some DNA bases sticking out from the fragment and can easily hybridise (blunt ends generally can't)
Sticky ends provide a greater surface area for bonds to occur and DNA to hybridise. Blunt ends can only form covalent, phosphodiester bonds where as sticky ends can form both covalent and hydrogen bonds with a foreign DNA sample. Also, as DNA ligase is needed to anabolise the backbone of DNA, using sticky ends will be quicker too (I guess?) because DNA ligase would work more efficiently (the two DNA strands would have already hybridised due to hydrogen bonds, therefore successful collisions between the enzyme and recombinant DNA would occur more frequently). I've gone a bit chemistry, but that might help clear things up? :)
Is heat shock a type of delivery mechanism?
Is heat shock, in which a plasmid is taken up by a bacterial organism an example of gene delivery systems? Thanks.
The gene delivery system is the plasmid and the whole shabang. Heat shock is just one of the steps involved in the gene delivery. The plasmid itself is the delivery system.
Why is heat used to separate DNA strands during PCR?
in the polymerase chain reaction, why is it that heat is used to split the two strands of DNA? Can DNA helicase be used instead to make two DNA strands?
In order to split the two strands of DNA, the DNA need to be denatured at a temperature high enough to allow the strands to separate (at 95 degrees). I think the reason why they do not use DNA helicase is that the whole process would not occur fast enough (in comparison to simply using heat) to amplify multiple copies of DNA or that they are unable to obtain DNA helicase from bacteria that are able to withstand the high temperatures that occur during the PCR process ( TAQ DNA polymerase is used in the process and is found in bacteria that thrive in hot springs.)...Though my assumptions could be wrong!
What is the purpose of recombinant DNA?
Also, what is the purpose of recombinant DNA?

To manipulate genes (kind of generic as it has several purposes)
Why are STRs used in gel electrophoresis?
In gel electrophoresis, are short tandem repeats the only DNA fragments that are used? If so, then why is this the case- why can't all DNA fragments be tested?

Thanks! :)
STRs are good because they give you fragments and because they mutate relatively quickly (no selective pressures). Most of human DNA is identical to other human DNA, so these sequences give you enough variation to deliver a meaningful result.
How does DNA ligase work?
How is DNA ligase used to create recombinant DNA?
DNA ligase basically acts as glue and joins the cut plasmid vector with gene of interest (which'll both have complementary sticky ends because they were cut from the same restriction enzyme)
Why do we need a control lane in gel electrophoresis?
How do you determine the length of a DNA molecule from Gel Electrophoresis? If we have a clear scale at the side, why do we need a standard/control DNA lane?
I think you need a standard with fragments of known sizes because agarose gels can differ slightly
Load DNA fragments of known length into one of the wells as a control. That way you known which DNA fragments make up each of the bands produced.
And we might not always let the fragments run for the same amount of time
Why can some bacteria take up recombinant plasmids, but others can’t?
Why do some bacteria take up plasmids and transform while others do not?
The bacteria need to be made competent to take up the plasmids (eg. with heat therapy). If this doesn't happen for a particular bacterial cell, it won't take up the plasmid
How do you tell if a person is homozygous or heterozygous for an allele from a gel electrophoresis?
How do you tell heterozygous and homozygous, and alleles on gel electrophoresis?

Homozygous: one band
Heterozygous: two bands
What type of bonds does DNA ligase help form?
So DNA ligase is used to catalyse the formation of phosphodiester bonds between restriction fragments?

And the hydrogen bonds between complementary nucleotides, form naturally? Without the aid of DNA ligase?
What is the buffer in gel electrophoresis?
What exactly is a buffer that is used in gel electrophoresis?

The buffer allows the current to be carried and helps to stabilise the pH as well
What does it mean when there are two identical bands in gel electrophoresis?
When referring to the results of gel electrophoresis, what does this question mean?

'Are there any two banding patterns that are exactly alike? How would you explain this?'
Two banding patterns that are exactly alike would have travelled the same distance within a given time period. This is because they are of the same length, and therefore their rate of travel would be identical.
Thanks, so it's just another way of saying the gel electrophoresis showed 2 matching DNA samples ?
Essentially, yes :)
Why does DNA need to be cut up before it can be analysed?
Why does DNA need to be cut up by restriction enzymes before analysis?  :)
So a specific gene or area can be observed and studied.
How can plasmids be used as a gene delivery system?
Under the SD dot point of DNA tools and techniques (AOS 1 outcome 1 unit 4) it says using plasmids as gene delivery systems as a DNA tool/technique

can someone explain this? how can plasmids be used as gene delivery systems?

thanks in advance
Whack a gene into a plasmid using restriction endonucleases and then whack the plasmid into a cell. That's pretty much the detail you need to know. Perhaps you also need to be vaguely familiar with the fact that the gene from the plasmid can end up in chromosomal DNA
What temperatures are used in PCR?
What temperature is a PCR mix raised to? There are several degrees so does anyone have a definite? Thanks.
I would say 95 degrees for denaturing, 55 degrees for extending, and 72 degrees for extension.
How does PCR work?
PCR is an abbreviation for Polymerase Chain Reaction. This reaction is used for DNA amplification; so we have a small sample of DNA and want to make, literally, millions of copies of this sample. PCR is the way to go. This method involves three stages:

Denaturation: The double helix DNA strand is denature, that is, the hydrogen bonds between the bases are broken as the sample is exposed to ~94 degrees Celsius. The bonds are broken and this will leave us with two single stranded DNA molecules with complementary bases.

Annealing: The temperature is dropped significantly and DNA primers are added to the solution so that they can bind to their complementary bases at either end of the single stranded DNA molecules. These primers act as 'starting points' for the synthesis of the new DNA. The primers bind at the 3' end of each single stranded DNA.

Extension: The enzyme DNA polymerase synthesises new DNA strands on each single stranded DNA (that was earlier broken into two) by attaching nucleotides to the exposed complementary bases. The DNA polymerase bases off the primers, and so synthesises the new strands of DNA in the 5'-3' direction. 
These are copy+paste from my notes on PCR

The process of Polymerase chain reaction (PCR) allows for the production of mass quantities of genetic material from a minute starting quantity. PCR can be used for medical applications (testing for genetic mutations) and in forensics.
The process of PCR revolves around the repetition of 3 main parts;
- Denaturation 
- Annealing and
- Elongation
During the denaturation stage; the DNA is heated to temperatures of around 90C in order to break hydrogen bonds between the adjacent DNA strands
During the annealing stage; Primer's (composed of short synthetic DNA strands) with nucleic acid sequences complementary to a portion of the DNA strand hybridize to their corresponding segments of DNA. Temperatures of around 55C are used during this stage
During the elongation stage; DNA polymerase (TAQ polymerase) binds to a forward/reverse primer and begins to synthesis a new strand of DNA using nucleotides found in solution, with a base sequence that is complementary to the template DNA strand. Temperature of 65C are used for optimal enzyme activity.
These three stages are repeated consecutively with the quantity of genetic material increasing in accordance with the exponential function 2^n, where n= number of times process is completed
What is gel electrophoresis?
Gel electrophoresis:
This is a technique that is used to separate and identify molecules of DNA or proteins. In your example, it would be DNA observation. Basically, electrophoresis separates different sized molecules of DNA, based on their amounts of base pairs (hence their sizes). This is done by pouring an agarous solution in the container, and inserting a comb into one end of the container. Once the gel has solidified, the comb is removed and a number of wells are created. An electric current is switched on and the positive end is at the far end of the wells, whereas the negative end is at the origin (or starting point, where the DNA molecules are placed in the wells). Now you should know that DNA has an overall negative charge due to the negative phosphate group in the sugar-phosphate backbone. This overall negative charge will allow the DNA molecules to move from the negative end, in which where they are initially placed, and move/migrate towards the positive end, as positive attracts negative. The DNA molecules all move at the same time, however, the smaller the DNA molecule (less base pairs/nucleotides), the farther it will move. The larger the DNA (the more base pairs/nucleotides), the slower it will move towards the positive end. At the end of a certain time period, the relative positions of the DNA molecules in each well can be used to determine the size of it.
These are copy+paste from my notes on Gel Electrophoresis
Electrophoresis is used to obtain a genetic profile and has many applications such as in paternity testing, and forensics
Electrophoresis separates DNA strands on the basis of length(size/mass)
Electrophoresis is usually performed after PCR has been completed
Genetic material is first subject to restriction enzymes which cuts the DNA sequence in accordance to their recognition sequences (I'm not sure if this step is performed before or after PCR has been completed)
DNA samples from the subjects alongside a control/standard (for size measurement) are suspended inside holes (made by a comb) within an agarose gel plate
A negative terminal is placed adjacent to a positive terminal on either side of the agarose gel plate. The DNA samples are located at the negative terminal
Current is switched on, and segments of DNA from each subject proceed to move towards the opposing pole at a pace in accordance with their size and charge
After a suitable period of time, current is switched off and a DNA profile from each subject can be obtained, and matched if required
What are DNA probes and DNA sequencing?
Can someone explain DNA probes and DNA sequencing for my sac tomorrow  ???
DNA sequencing identifies the exact order of bases in a DNA molecule. 
It uses a single-stranded DNA template to make lots and lots of copies of the DNA, working like PCR except with an extra step, termination.
You could memorise the 4 main steps with the acronym SEAT:
•   Separate DNA strands
•   Anneal primers
•   Extend primers
•   Terminate strand
How is the strand terminated?  You add dideoxynucleotides to the mixture.  They’re DNA nucleotides missing a hydroxyl group on their 3’ end, so they can’t bond with the next nucleotide.  Each of the 4 different dideoxynucleotides is labelled with a different dye.  Occasionally, the taq polymerase builds a dideoxynucleotide into the growing strand, stopping the strand.  You organise how soon the dideoxynucleotide is added by carefully controlling the concentration of dideoxynucleotides to normal nucleotides.

The aim of this is to get lots of copies of the DNA strand, each copy one nucleotide longer than the last.  So, the first one with a primer plus one nucleotide, the second a primer plus 2 nucleotides, the third a primer plus 3 nucleotides, and so on.  And the last nucleotide in each chain is always a dideoxynucleotide with a dye marker attached.

Then, you send your copies through gel electrophoresis which orders them by length; in order, they pass a laser which records the dye colour attached to each copy and thus records which base is the last base in the strand.

So, the first scanned strand is the primer + 1 nucleotide, and that one nucleotide is recorded.  The second is the primer + 2 nucleotides, and the second of those nucleotides is recorded.  And so on, until the sequence of the whole segment is recorded!
So, with DNA sequencing, you use PCR with termination by dye-labelled dideoxynucleotides to produce lots of DNA strands each one longer than the last.  You then sort them by gel electrophoresis, and by detecting the dye colour in order, you can tell the whole sequence!
How do restriction enzymes cut plasmids?
How do plasmids become cut open by restriction enzymes? because doesn't bacterial dna have methyl caps on it to stop its own restriction enzymes damaging it whilst fighting against viruses and the like? I'm guessing that you use restriction enzymes from other bacteria that are not naturally present in the bacterium of interest to cut open plasmid, since the plasmid would be resistant to its own restriction enzymes yeah? Thankyou
Restriction enzymes recognise specific DNA sequences located on the DNA molecule (plasmids in this case). When this recognition site has been identified, the enzyme cuts the specific sequence. I am assuming that a different restriction enzyme, that recognises a different sequence is placed into bacterias and that cuts out the plasmid, so that the desired gene can be joined on to the plasmid using DNA ligase. I think you are thinking too deep into it, but you are definitely right, good question xD
What do endonucleases do?
3)what do restriction endonucleases do/ endonucleases in general?
3) Restriction endonucleases is another term for restriction enzymes. They simply cut genetic material at binding sites. They are commonly found in bacteria as a mechanism at protection against viruses (destroy their genetic material before it can be incorportated in the bacterias own). They can be used in gene manipulation and gel electrophoresis (fragment the DNA)
What temperatures are used during PCR?
What are the temperatures that are used in PCR? Every book is telling me different, is it 94•C/93C then 55 or 50C then 72C?
4. They're not exact. It actually depends on what primers you're using, hence the slight differences. You only need to know them roughly
Why do we need to add individual nucleotides to PCR?
1) why do we need unique nucleotides in PCR?
1. Not sure what you mean by unique nucleotides. Individual A, T, C, G nucleotides have to be added, they are then joined onto the end of the primer by the taq polymerase effectively creating another strand. The taq polymerase just adds nucleotides, it does not create them so you have to put them in yourself. Does that answer your question?
How can Short Tandem Repeats be used for DNA profiling?
2) How can the Alu repeat regions (in gel electrophoresis) be used for DNA profiling?
2. Gel electrophoresis sorts fragments according to length. Individuals with more Alu repeats will therefore have longer fragments, which you will able to see when looking at a gel electrophoresis. If DNA from a crime scene is compared to two suspects and one suspect has a fragment of the same length as the crime scene DNA then they are likely the criminal.
What are short tandem repeats (STRs)?
Could someone explain to me what STR(short tandem repeats) are I just don't understand what they are and what they do?
Just repeats of a small sequence of code (2-5bp). So it may just be TATATATATATATATATATATATATATATATATATATATATATATATATATATATATA

So you've got lots of short repeats that are together in tandem. They're mainly in the non-coding regions of DNA. They're useful in pedigree analysis because they're easy to probe and the mutation rate is a little bit higher for these regions. Therefore, they're more polymorphic (more varied) than other sites of the genome.
What’s the difference between GMO’s/transgenic organisms/knock-out/knock-in organisms?
So we have just started on area of study 2 of unit 4, and I'm kinda confused :o
Can somebody please explain to me the correlation between GMO's and transgenic organisms, and knock-out/in organisms?
Are transgenic organisms a type of GMO?
And are knock-in and knock-out organisms classified as GMO's or transgenic organisms or what?

Sorry...just trying to get my head around the topic before we head back into term 3 ;)
You never need to apologise for asking questions :)

I never actually learnt about knock in or knockout organisms, it’s not mentioned on the study design but if your teacher is telling you about them then you should learn them for your SAC.

A GMO is a genetically modified organism - regardless of the type of modification.

A transgenic organism is one that contains a gene from a different species.

A transgenic organism is a type of GMO, but not all GMO’s are transgenic.

I tried to look up knock in and knock out organisms, but what I found was contradictory. They are definitely GMO’s, however I’m not entirely sure if they are transgenic - perhaps it depends on the individual case. If you get a question on them it will probably be in a scenario so it should tell you. If it has a gene from another species it’s transgenic, if it’s just had random DNA inserted/changed it’s a GMO, but is not transgenic.
Is genetic engineering a form of mutation?
Google: In biology, a mutation is the permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA or other genetic elements.

So does that mean genetic engineering is a form of mutation?
No, genetic engineering is not a form of mutation. Mutations occur either spontaneous via random errors in DNA replication or induced via mutagens (e.g. radiation) when DNA fails to repair itself when a fault occurs in the nucleotide sequence (DNA constantly undergoes changes and errors, however most of these are repaired and in the rate circumstance that they aren't, they form mutations) => Mutations are indeed a permanent alteration in the nucleotide sequence, however they result from the failure of DNA repair
What is the function of primers in PCR?
What is the function of primers in PCR?
The function of primers in PCR is to act as a starting point for taq polymerase to build off.
What length palindromes do restriction enzymes cut at?
Just wondering, do restriction enzymes cut at recognition sites of 6 or 4-8 base palindromes?
My textbook (nelson) and connect notes said 4-8, however edrolo said 6.
Is it just that 6 is most common, however it can cut at 4-8?
Yep. 6 is just the most common
Are transformed bacteria considered a transgenic organism?
If a bacteria successfully takes up a recombinant plasmid, it is considered to be a transformed bacteria. However, would it still be correct to call the transformed bacteria a transgenic organism, as it contains DNA from an organism belong to a different, unrelated species.
Yeah, that's what we were told.
What’s the difference between recognition site/recognition sequence/restriction site?
[quote author=Scribe link=topic=151609.msg1058905#msg1058905 date=1535267222
What is the difference between recognition site, recognition sequence, and restriction site? Are these terms interchangeable? I'm unsure as to what they mean in terms of endonucleases.
Yes, they mean the same thing! And they relate to restriction endonucleases or restriction enzymes, not just endonucleases. This is because they cut the DNA at specific points or recognition sites etc
Do restriction enzymes cut covalent or hydrogen bods?
Do restriction enzymes cut the hydrogen bonds between nitrogenous bases as well as the covalent bonds in the sugar-phosphate backbone? Just wanted to clarify bc I've read a few sources online where some say restriction enzymes only cut covalent bonds but others say they cut both.
Restriction enzymes only cut the covalent binds, a few hydrogen bonds aren’t strong enough to keep the strands attached so they seperate too. This is also why sticky ends are called sticky - the hydrogen bonds temporarily bind ‘stick’ long enough for ligase to create covalents bonds whereas blunt ends up less likely to be reattached because they won’t join each other.
What’s the purpose of primers in PCR?
What exactly is the purpose of the primers in PCR?
So they attach to the complementary DNA strand, but why???
So you have a starting place for the polymerase to act on. The primers usually anneal just outside to the section of DNA that we want to amplify.
Primers act as a binding site for Taq  polymerase, as otherwise Taq polymerase cannot attach and complete the 3rd step of PCR: extension
« Last Edit: November 27, 2018, 02:23:21 pm by PhoenixxFire »
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Re: Biology Q&A archive/Bio FAQ
« Reply #16 on: October 14, 2018, 09:51:29 pm »
U4 AOS 2 Biological knowledge and society
Relevant study design dot points
• techniques that apply DNA knowledge (specifically gene cloning, genetic screening and DNA profiling) including social and ethical implications and issues

• the distinction between genetically modified and transgenic organisms, their use in agriculture to increase crop productivity and to provide resistance to insect predation and/or disease, and the biological, social and ethical implications that are raised by their use

• strategies that deal with the emergence of new diseases in a globally connected world, including the distinction between epidemics and pandemics, the use of scientific knowledge to identify the pathogen, and the types of treatments

• the concept of rational drug design in terms of the complementary nature (shape and charge) of small molecules that are designed to bind tightly to target biomolecules (limited to enzymes) resulting in the enzyme’s inhibition and giving rise to a consequential therapeutic benefit, illustrated by the Australian development of the antiviral drug Relenza as a neuraminidase inhibitor

• the use of chemical agents against pathogens including the distinction between antibiotics and antiviral drugs with reference to their mode of action and biological effectiveness.

What is the difference between gene therapy and gene transfer?
[quote author=millie96 link=topic=151609.msg777025#msg777025 date=1412553211
Is gene transfer the same as gene therapy?
Gene therapy is an application of gene transfer
What do we need to know about rational drug design
How much do we need to know in terms of rational drug design?
Probably just how a drug can be produced with a SPECIFIC COMPLEMENTARY shape to a substance or part of the substance (pathogen/enzyme) to inactivate its function :)
And that they're designed to target a specific enzyme so as to kill a microorganism/cure a disease. The whole point of rational drug design is that you find a particular enzyme target and then knock it out by inhibition.
The fact that the structure of a particular enzyme's active site needs to be identified. A potential inhibitor, complementary to the active site of the enzyme is created. This is then exposed to the enzyme via injection or other means of delivery system. This 'inhibits' the enzyme's functionality as substrate is blocked out, meaning the artificial drug is successful and efficient.
How do gene probes work?
How do gene probes allow you to find a particular gene?
I know that they are "labelled", that is with a fluorescent dye or a radioactive label, but when it is inserted, does the target gene become visible because of the label (gene probe)?

Thank you :)
Yes because DNA is a clear substance. However, the probe will only fluoresce under UV light.
What’s the difference between recombinant DNA and a transgene?
What's the difference between 'recombinant DNA' and a 'transgene'?
Well the difference between the two is that, transgene is a gene that is not native/belonging to an organism (a gene that is transferred from one organism to another) whereas recombinant DNA is DNA that has essentially been combined with other, different DNAs (manipulated DNA - contains more the one organisms' DNA).

An easy way of remembering it is that DNA is double-stranded right? So during recombination, the strands are unzipped into two, thus allowing another strand to bind with either of the original strands (aka. a transgene) resulting in recombinant DNA.
Pro’s and con’s and ethical concerns of artificial selection and gene therapy
Can someone list the pro's and con's (and ethical concerns) of artificial selection/domestication/selective breeding and also gene therapy?
Artifical selection/Selective Breeding:
1.) Aesthetic appeal
2.) Economic value (higher crop yields, shorter harvest time etc)
1.) Lack of genetic diversity which could lead to the loss of disease-resistant alleles, hence increasing the susceptibility of the organisms to disease.
2.) Continuation of traits which are disadvantageous for survival/reproduction
e.g. English bulldogs have been selectively bred to maintain a 'pure line' but their shortened muzzles and flattened faces cause respiratory problems. So many features artificially selected for can be detrimental to the survival of the organism.

Genetic modification:
1.) Can permanently alter the genotype to produce "ideal" phenotypes.
2.) Can reduce the use of toxic insecticides in crops.
e.g. In Bt corn the corn has been genetically modified to produce insecticidal proteins protecting it from many of its pests and this reduces the use of toxic insecticides.
1.) Unwanted gene flow between GMO's and non genetically modified organisms: unwanted spread of GMO's.

Hope that helped. Sorry don't know much regarding ethical issues.
What’s the difference between gene therapy and gene transfer?
Is gene transfer the same as gene therapy?
Gene therapy is an application of gene transfer
How much do we need to know about rational drug design?
How much do we need to know in terms of rational drug design?
Probably just how a drug can be produced with a SPECIFIC COMPLEMENTARY shape to a substance or part of the substance (pathogen/enzyme) to inactivate its function :)
And that they're designed to target a specific enzyme so as to kill a microorganism/cure a disease. The whole point of rational drug design is that you find a particular enzyme target and then knock it out by inhibition.

The fact that the structure of a particular enzyme's active site needs to be identified. A potential inhibitor, complementary to the active site of the enzyme is created. This is then exposed to the enzyme via injection or other means of delivery system. This 'inhibits' the enzyme's functionality as substrate is blocked out, meaning the artificial drug is successful and efficient.
What’s the difference between transformed and transfected?
What is the difference between "Transformed" and "transfected" ?
It's supposed to be that transformation involves bacteria and transfection involves eukaryotic cells, though in reality nobody adheres to this distinction. Both are normally used interchangeably.
What’s the difference between artificial selection and natural selection?
Can someone list a few differences and similarities of artificial selection and natural selection?
Artifical selection is when humans intervene and selectively breed desired individuals
Natural selection is the natural process of "survival of the fittest" where natural selective pressures result in fit individuals thriving
What’s the difference between genetic testing and genetic screening?
Hey, can someone please clarify the difference between genetic testing and genetic screening.
Thanks in advance!!
Test: I want to test you for this disease because I think you might have it
Screen: I'm gonna test a whole bunch of people and hopefully find someone with the disease
Social and ethical implications of DNA profiling and gene cloning
Hey everyone
What's the difference between social and ethical implications?
And what kind of social and ethical implications exist in gene cloning and DNA profiling?

Thanks in advance!
Social: Effects people. eg. Not all farmers will be able to afford a GM crop
Ethical: Just bad (at least to some people). eg. Humans shouldn't be allowed to interfere with nature - 'playing god'

For DNA profiling

-If you find out that you have a genetic disorder that means our parent does too.(eg Huntingtons - something you don't find out until later in life)
-Not everyone will be able to afford DNA profiling
-May be charged more for life insurance
-May lose/not get job due to possible inability to work in future

-Should you be allowed to find out if there's no treatment
-When used in embryo selection it alters our gene pool.

There's plenty of others but that's just what I came up with. I'm sure there's some that fit into both as well.
The differences between "social" and "ethical issues can be hard to determine, as they overlap a lot, but here's a brief distinction:
- ethics is about right or wrong actions, for example: breeding and planting GMOs, or claiming genes as intellectual property.
- social issues tend to be more specific towards the effect of an action on people, and society in general, for example: the effects of selling GMOs to the public, stuff like that.
- you can talk about them as if they are a single unit tho, nothing wrong with that.
Here are some social and ethical implications of DNA profiling (+ pros, - cons)
+ regular health monitoring of individuals can be implemented, and preventative action can be taken on individuals with genetic disorders/diseases.
+ couples can plan their pregnancy, and make preparations based on the results of DNA profiling/screening for their child
+ a negative result on screening/profiling in relation to genetic diseases can often reduce emotional stress
- a positive result of a genetic disease may induce stress, and can be an emotional burden
- DNA profiling and genetic screening can hinder with one's privacy
- DNA profiling and genetic screening can often be inconclusive, and data can be difficult to interpret
Social and ethical implications of genetic cloning (and also genetic engineering technology which produces GMOs)
+ producing enhanced crops, and organisms, which translates to technological advancement
+ higher quality of life
+ alleviate poverty (higher yielding crops)
+ reduce the detrimental effects of diseases (check out golden rice, transgenic rice with beta carotene which turns into vitamin A, to aid with vitamin A deficiencies within poorer nations)
- genetically modified organisms or cloned genes may affect ecosystems as gene flow might occur between natural and modified organisms (some genes may result in a selective advantage, which affects the allele frequencies of populations)
- companies might claim segments of genes as intellectual property (unethical), and charge high prices for any research/development involving the specific gene.
- GMOs can affect the production of traditional food, and might or might not be adequate substitutes for these traditional food items in providing the required nutrition.
- thorough, rigorous and independent testing of GMOs are required to ensure that the segments of cloned genes do not affect the quantity of production, and gene flow between modified and natural populations that can lead to devastating consequences.
How are GMO’s used in agriculture?
How are GMOs and transgenic organisms used in agriculture to increase crop productivity and to provide resistance to insect predation and/or disease?
GMOs and trangenic organisms (transgene is a type of genetic modification) are organisms which contain genetic material from other sources (usually organisms of other species, which makes a GMO a transgenic organism). For plants, this could mean that one can modify a specific section of a gene within the plant to increase its crop yield, which in turn increases their crop productivity in agriculture. Sections of genes which codes for resistance towards pests, weeds and microbes can also be inserted within the genome of an organism (these genes may be expressed and a protein or toxin could be produced to fend off these pests, weeds and microbes).
LifeisaConstantStruggle beat me to it whilst i was typing but i will add this,

There are two main ways that insect predation is stopped. They are given a gene that makes them resistant to insecticide/herbicide, they can then be sprayed a lot, killing the pests but not the plant. Or they produce a protein (eg. Bollard cotton) so that, when an insect eats the plant, the protein will kill them.

Also worth noting that genetic technology can be used to identify a crop's genotype - deciding which should be used in the next generation, which is more accurate than relying on phenotypic characteristics (ie. normal selective breeding). This is used a lot, especially with cattle for milk production but these organism have not been altered so they are not GMO's.
How much detail do we need to know about social/ethical issues surrounding gene technology?
how much detail do we need to know about the ethical and social issues surrounding gene tech?
For the exam you need to be able to list and very briefly describe a few positives and negatives of gene tech in terms of how it benefits society and also be able to describe a few social and ethical issues that might arise from its use. You won’t need to memorise entire lists or anything like that.

For your SAC it might be a bit different though. It really depends on your teacher, for mine I had to know about one issue in depth. If your teacher doesn’t tell you in advance to learn about a specific issue/give you handouts on it then the above should be enough.

I doubt it will be assessed in detail on the exam, you’ll probably get a question in relation to a specific scenario.
How do bacteria become resistant against antibiotics?
How does bacteria become resistant against antibiotics when people overuse or misuse them?
In your question, we can apply Darwin's theory of evolution and natural selection. So in the population of bacteria, there will already be variation in the population. Therefore, there may exist certain bacteria which are somehow different and are resistant to the antibiotics (due to a random mutation). Then when a person uses antibiotics, it acts as a selective pressure. All of the bacteria without the resistance will die while a small amount of bacteria resistant ones will remain (they have a selective advantage). So when you overuse the antibiotics, you will kill all of the non-resistant ones leaving the resistant ones to breed with each other and they will increase in numbers slowly and then eventually when you try to cure the same infection with the antibiotics, most of the bacteria will be resistant
As well as natural selection, antibiotic resistance can be spread between bacteria. Genes for antibiotic resistance are commonly found on plasmids. Plasmids can be transferred between bacterial species, effectively giving more and more bacteria the resistant gene.
What do we need to know about emerging diseases?
What should we know about emerging diseases for the exam?
•    strategies that deal with the emergence of new diseases in a globally connected world, including the distinction
between epidemics and pandemics, the use of scientific knowledge to identify the pathogen, and the types of
My interpretation of this is that you don't need to actually know about emerging diseases as such, you just need to know about how to identify pathogens and treatment options.
What should we know about types of treatments for pathogens for the exams?
What should we know about types of treatments for pathogens for the exams?
4. Just need to know about antibiotics/antivirals/etc. including what type of pathogen they can be used against.
Which DNA profiling techniques do we need to know?
So I'm a little confused with DNA profiling - some of the resources I have mention STR's only, whereas others mention VNTR's, and others mention RFLP's... are they all the same process or are they different? And do we need to know all for the exam?
VNTRs and STRs are actually the same thing it's just an arbitrary distinction between the length and quantity of those repeats (STRs being shorter and less repeats).
RFLPs are restriction fragment length polymorphisms so depends on certain restriction enzymes and where they cut.

Make sure to check the study design if you are unsure if anything is required/not required.
What do we need to know about transgenic crops?
Hi guys, what exactly do we need to know about transgenic crops in this SD dot point?

- The distinction between genetically modified and transgenic organisms, their use in agriculture to increase crop productivity and to provide resistance to insect predation and/or disease, and the biological, social and ethical implications that are raised by their use

Do we need to know how they are made or any examples? Thanks :)

For that dot point you don’t need to know how they’re made, but I think there’s a different one that refers to it? You do need to know a bit about how they’re made in order to distinguish between transgenic and gmo though.

You don’t need to know an example for the exam however you might have to for your SAC (I did).

You need to know:
-definitions and differences between transgenic and GMO’s
- their use in agriculture (making crops bigger, making insect that eat them die, making them resistant to insecticide/pesticides so that more can be sprayed on them)
-biological issues - things like wiping out natural plants
-social issues - e.g. farmers who can’t afford the modified plants going bankrupt
-ethical issues - e.g. ‘playing god’
Why do we use STR’s for DNA profiling?
Why do we use STR regions for DNA profiling?
They're highly variable regions, so the chances of peoples being the same are low - hence they can be used to create a unique DNA profile (sort of like why we use fingerprints)
Why does not finishing a course of antibiotics contribute to antibiotic resistance?
Can someone please explain to me why not finishing a course of antibiotics contributes to antibiotic resistance?
Bacteria can be partially resistant to antibiotics, meaning that the antibiotics aren't quite as effective as they would normally be. So if you only use half the course, you only half kill the bacteria, and then the partially resistant bacteria grow back and then constitute the bacteria that get passed around, then they can evolve to become fully resistant.
What’s the difference between gram-negative and gram-positive bacteria?
Can somebody please explain the difference between gram negative and gram positive bacteria? Do we need to know this for the study design?
Thanks ;)
Gram staining is to classify whether bacteria have peptidoglycan present in their cell wall or not. Gram positive means that they do have peptidoglycan present, and gram negative means that it is not present. This is useful to know, as bacteria with a certain cell wall composition can be more susceptible to certain antibiotics. And yes, I believe this falls under " the use of scientific knowledge to identify the pathogen" on the study design
Can rationally designed drugs be treated as foreign by the immune system?
I've got a few more questions.
1) Can rationally designed drugs be detected as foreign and treated as antigens by the immune system?
1. I'd imagine not. I mean, it's possible but they're very small molecules and they're not cells/don't produce proteins like bacteria/viruses. (Definitely not for VCE)
Can antisense mRNA be a type of rationally designed drug?
2) For the context of VCE biology, can antisense mRNA being used as a silencer be used as a form of 'rationally designed drug' or does that fall under a different category?
2. For VCE, no. A rationally designed drug is one made specifically to fit into a molecular shape, for VCE you just need to know about enzyme inhibitors.
study design
the concept of rational drug design in terms of the complementary nature (shape and charge) of small molecules
that are designed to bind tightly to target biomolecules (limited to enzymes) resulting in the enzyme’s inhibition
and giving rise to a consequential therapeutic benefit, illustrated by the Australian development of the antiviral
drug Relenza as a neuraminidase inhibitor
What is ELISA and why is it used?
3) What is ELISA and why is it used?
Not 100% sure on the other ones, so I will leave them for someone else, but for ELISA...
ELISA (Enzyme-Linked Immunosorbent Assay) is a technique that uses an antibody-enzyme complex. The antibody section of the complex binds with the pathogen antigen. The enzyme ‘s usual substrate is then added and reacts with the enzyme, producing a colour change that can be detected.
The process is as follows:
1.   Antibodies for the suspected antigen (of the pathogen) are added to the bottom of a well
2.   The blocking agent is added to fill any areas not bound by the antibody.
3.   Swabs from a patient’s sample are added. If the antigen is present in the sample, it attaches to the antibody. If the antigen is not present in the sample, it does not attach to the antibody.
4.   An antibody with an enzyme attached is added. If the antigen has attached to the antibody, this second antibody attaches to the other end of the antigen. If the antigen has not attached, this second antibody does not attach either.
5.   The plate is treated is that the solutions in the wells turn a particular colour only in the presence of the antigen-antibody complex.
Note: between each of the above steps, a washing step occurs to remove any loose particles.
The strength of the colour indicates the quantity of antigens present. The darker the colour, the more antigens are present, and therefore the more infectious the person is.
(Sorry... just copied it directly from my notes so hopefully it makes some sense :o )
« Last Edit: February 27, 2019, 09:53:17 am by PhoenixxFire »
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Re: Biology Q&A archive/Bio FAQ
« Reply #17 on: October 14, 2018, 09:53:33 pm »
U4 AOS 3
Key knowledge dot points
• independent, dependent and controlled variables

• the biological concepts specific to the investigation and their significance, including definitions of key terms, and biological representations

• the characteristics of scientific research methodologies and techniques of primary qualitative and quantitative data collection relevant to the selected investigation, including laboratory work (biochemistry, cytology, immunology) and/or fieldwork (geomorphology); precision, accuracy, reliability and validity of data; and minimisation of experimental bias

• ethics and issues of research including identification and application of relevant health, safety and bioethical guidelines

• methods of organising, analysing and evaluating primary data to identify patterns and relationships including sources of error and limitations of data and methodologies

• models, theories and classification keys, and their use in organising and explaining observed phenomena and biological concepts including their limitations

• the nature of evidence that supports or refutes a hypothesis, model or theory

• the key findings of the selected investigation and their relationship to cytological, biochemical and/or evolutionary concepts

• the conventions of scientific report writing and scientific poster presentation including biological terminology and representations, standard abbreviations, units of measurement and acknowledgment of references.
How to answer experimental design questions
How do you guys tackle experimental design questions? What's your "formula"?
-Use keywords such as 'experimental' and 'control' group.
-Maintain similar environment for all (temp, pH, humidity,diet, etc)
-Maintain large sample size.
-Make sure to duplicate the experiment multiple times if necessary.
-Use participants that are usually of the same age, health, status, etc.
-Might want to state how experiment could be improved.
-State whether experiment was supported/negated and ALWAYS make comparative statements.
-What are you testing? What are you aiming to prove? (i.e. hypothesis)
-Large group, controlled environment
-Describe how your experiment will go...does it prove what you're looking for? How can you draw conclusions from it?
-What conclusions will support your hypothesis? What conclusions won't?
Which is the independent/dependant variable?
Can someone pleeease help me with this..

I get confused between independent and dependent variables.

Say in an osmosis experiment involving potato pieces in a salt water concentration,
what is the independent variable and what is the dependent variable?
Is it true to say that a controlled experiment can have many dependent variables but only one independent variable?

If I were to observe what would happen to potato pieces in three beakers (A, B and C). (Note beaker A contains dilute water, beaker B contains 2.5% salt and beaker C contains 5% salt), what would be a good hypothesis for this?

Thanks!!  ;D
In an experiment, for eg the potato experiment, in order to get the diluted and concentrated solution, you must add salt to each beaker, hence, you can change the concentration of salt whatever you want, you can add more, you can add less, it's all up to you. Hence, we call the concentration of salt the INDEPENDENT VARIABLE. Since the external environment will determine the net movement of water in or out of the potatoes cells, we call the net movement of water the DEPENDENT VARIABLE since it is caused by the concentration of substrate outside. In practice, it is actually really hard to make sure that all the other variables constant and ONLY the independent and dependent variables that change, hence, we have to minimize as much as possible the changes in all other variables except independent and dependent variables.
A good hypothesis is all about making a measurable and observable hypothesis, you have to be specific about your quantities. Hypothesis is usually an " If....then..." statement.  Hence, my possible hypothesis for this is, " If the concentration of salt on the external environment changes in an addition of 2.5% then, there will be a net movement of water from the potato cells to the external environment (a hypertonic environment) by osmosis effect, hence, there will be a decrease in mass of the potato due to the loss of water content"
Hope this helps.
Hey, I had the same prac  :D

I mentioned that the independent variable was the salt concentration and the dependent variable was the mass of the potato tuber cells (if you used the 'weighing method'). Yes, there can be more than 1 dependent variable in an experiment but, for this experiment, you should only be investigating one DV. For example, in another experiment, if you were investigating the effect of catalase on hydrogen peroxide, the dependent variable could be the height of oxygen bubbles and/or the number of oxygen bubbles that formed when catalase was reacted with hydrogen peroxide. However, you will most likely only measure and compare the height of oxygen bubbles as it's much more difficult to count the number that form. So, my point is: even though there may be more than one DV, you only mention how many you tested (mostly likely 1 or 2). Also, it's important to know that the whole purpose of control variables is to know that your independent variables don't act in isolation (so you know that there isn't any other factor affecting them during the experiment).
What variable do we write if it doesn’t specify?
If an experimental report asks us to write a variable in the experiment but doesn't specify whether we should write independent or dependent variable, then what should we write?
I would mention both the independent and dependent variables, but usually reports aren't that vague to not specify the variable they wanted you to describe.
If we repeat the experiment, do we say so in the discussion?
If we repeat the experiment, do we mention it in the discussion? If so, how? is it acceptable to say that the experiment was repeated?
I would mention both the independent and dependent variables, but usually reports aren't that vague to not specify the variable they wanted you to describe...
Yes, you would mention if you repeated the experiment in the discussion. You must also say why the experiment was repeated. The most obvious reason is to reduce experimental error.
What do ‘control’ and ‘variable’ mean in relation to a scientific experiment?
Can someone please explain to me what the terms  'control' and 'variable' mean, when referring to a scientific experiment?

Thanks!  :)
Variable - a factor that can impact on the outcome of the experiment
There are 2 types of variables:  Independent variable (one that is deliberately changed)
Dependent variable (one that is changed due to the change in Independent variable)
Controlled: usually "controlled experiment" which refers to an experiment in which everything is keep at constant and does not change EXCEPT only the independent and dependent variable. This helps to validate the changes those above variables really have an effect but not the other.
Hope this helps.
Why is big groups/identical groups/same conditions/controls important in an experiment?
Why is each of these things important:

Big groups
Identical or similar groups
Same conditions
Big groups: incase a portion of your sample doesn't work, dies, is corrupted or something of that sort occurs you have more samples too obtain results from.
Identical or similar groups: this is essential since results can be manipulated by external conditions and if they vary for different groups, results aren't accurate.
Same conditions: assurance that other environmental factors do not influence the response/results.
Control: for comparison and set standard.

I think.... :P
Yep, you're essentially there with most of it!

Big groups: this is to deal with the effect of randomness. So if you think about if you were doing a study on whether a drug causes heart attacks. You have a group of two people. One gets the placebo, the other gets the drug. The one with the placebo has a heart attack a week later and dies. What might you conclude from this study? You may conclude that the drug actually prevents heart attacks. I'm sure you can see why this conclusion is a little bullshit...there are any number of reasons why that person suffered a heart attack. So, by having larger groups, you help to reduce the effect of random events like that. Because if you've got really big groups, a random effect in one group is likely to be replicated in the other group. The bigger, the better group wise!

Identical/similar groups: when you're conducting an experiment, you want to draw a relationship between two variables (i.e. you're trying to work out whether A causes B). By making the groups identical, you limit any other factors that could cause the result you're looking for. E.g. if you're looking at whether a drug causes people to lose weight, and you put obese people in the weight loss group and skinny people in the control, then you've pretty much stacked your study...of course the obese people are going to lose more weight, they have more weight to lose!

Same conditions: same as identical/similar groups; to make sure that nothing interferes with the results

Control: exactly what you said, it's a standard against which one can compare a result.
What needs to go in the conclusion of a prac report?
What exactly goes into a conclusion of a prac report?

Is it true we need to reinstate our hypothesis and further expand on it?
Reinstate the aim of the practical, make mentions of the results and whether they support or do no support your hypothesis. That's it really. Two sentences should suffice.

Never add new information.
What is the purpose of a control group?
Hi there, what to write when explaining the purpose of a control group? I read in the Checkpoints that simply stating 'standard of comparison' is not good enough. I used to think that it is 'to ensure that the independent variable is the only factor causing a change in the reuslts', but I'm not so sure any more. Somebody help? Thanks  :)
I think your explanation is pretty good. For mine, a control group does serve as a point of comparison so that you can be more confident that your results are truly due to the effect of the IV, and not a confounding variable. I think, perhaps, it might be useful to explicitly state that the control should be, where possible, as similar as it can be to the treatment group and should be exposed to exactly the same conditions as the treatment group, except of course for the IV :)
What type of errors does repetition and averaging help with?
5) In scientific method, does replication and the obtaining of an average help reduce the effect of uncontrolled variables or errors (systematic)? Or is it both?
5) It wouldn't help for systematic errors that are present in all replications of the experiment, however it would help against errors that are in one experiment. Eg. If you used a thermometer measuring 5 degrees low in all of one experiment it would be a systematic error but if you repeated the experiment on another day and used a different thermometer that was working then it would only affect one replication of the experiment so its affect would be minimised through repetition, however if you used the same (broken) thermometer for all the experiments then repeating it would not help.
It's the same sort of thing. Repetition only helps reduce the effect of uncontrolled variables if they are not present in all repetitions. Any errors that are present in all cannot be minimised through repetition as you will continue getting the same wrong results, however errors that are not present in all can be minimised as some of your results are accurate.
Why is it better to have the % change rather than the raw data?
3. Percentage vs. raw: why is it better to have percentage change rather than raw data?
3. Percentage change is more accurate as all the samples may not be exactly the same at the start of the experiment. Eg. Doing an experiment on osmosis by measuring the weight of potato strips - you are not likely to be able to get all of them exactly the same weight so % change is more accurate - otherwise the results do not take into account the difference in the original weight.
What’s the difference between accuracy/validity/reliability/precision?
Can someone please explain to me the differences between accuracy, validity, precision and validity?

Accuracy: How close the found results (in the experiment) are to the ACTUAL theoretical value or known theory per se. (Accuracy, A = Actual)
Precision: How close the found results are to ONE ANOTHER.
Validity: In biology, this can be improved by using a CONTROL group to ensure the experiment is providing results based on what the experiment was INTENDED to find.
Reliablity (I believe this is what you meant): Again, in biology, this can be improved through repeating an experiment, ensuring the obtained results are CONSISTENT (and hence more likely true to theory)...
What’s the difference between accuracy and validity?
hey guys, could someone clarify the main difference between accuracy and validity? also if an experiment is accurate is it necessarily valid as well and vice versa??
Accuracy is whether you are correctly measuring something. ie if you measure something that is actually 1metre and get 50cm your measurements (and therefore results) are not accurate. Validity is whether you are actually testing what you're supposed to be testing ie have you designed an experiment that tests your hypothesis?
No, a test can be accurate (measured correctly) but not valid (not testing the hypothesis) and vice versa.
How do I design an experiment?
Not sure where to start for this question:

Design/Outline an experiment to test the effect of inhibitors on enzyme activity.
Basically it just wants to know your method, but in paragraph form (sometimes you can draw diagrams too).
You need to include
-controlled variables
-sample size
-control and experimental groups
Basically just include everything that you would need to know in order to run the experiment.
Questions about prac on catalase and hydrogen peroxide
Hello. Okay this is my first year ever doing biology, so i feel a little behind. I appologise for a long thing and all the questions. I'll number the questions.
We have completed 2 practical experiments on enzymes. The first one was testing the rate of reaction between Liver Catalase and hydrogen peroxide in 3 different pH buffers (4, 7 & 10).
The second one was testing the rate of reaction between Liver Catalase and hydrogen peroxide at 4 different temperature; Ice cold, room temp., 40 degrees, and 80degrees. Although, what we did was put the test tubes with Liver in water in a bath of each of those temps for 10 mins and then we had to let them all sit to return to room temperature. 1. So i'm guessing the aim wasn't to see how temperature effects the rate of reaction, but instead how temperature effects the enzyme in a way which in turn effects the reaction rate? Unless that's legit the same thing idk.

For both practicals, the ROR was tested using a stop watch, a ruler, and a splint. It wasn't specified exactly how to use those tools to measure.
I saw some students timing the reaction up until the bubbles started to dissappear. However i was timing how long it took for the bubbles to reach a maximum height. So i stopped timing when the bubbles stopped going higher and were instead building at the same rate as they dissappeared. 2. Not sure if that's a correct way of doing it?

Then,  i assumed that when the bubbles had stopped increasing in height that perhaps that meant the Enzyme was saturated. 3. But if each trial had the same amount of liver and the same amount of Hydrogen Peroxide then shouldnt all the trials have reached the same maximum height but just at different speeds? 4. Most trials had a height difference of between 0.2 and 1cm. Why didn't all the trials climb to the same height? Or is that due to varying degrees of enzyme denaturation?
5&6. Actually, if the bubbles stopped growing in height, could that mean that there is simply less hydrogen peroxide molecues floating around and so less collisions occuring instead of the enzyme being saturated? bc the substrate wasnt increased so i guess the enzyme wouldn't have become saturated?

So i know catalase optimal pH and temperature is 7 and 37 ish degrees right? But i think the reaction was quickest in the room temperature trial compared to the 40 degree one. Thing is, there are discussion questions on this, one of which asks to write the optimal pH and temperature. the pH everyone knows is 7, 7. but how could we know the temperature when the only trial that was close to that temp was the 40 degree one? I originally assumed the optimal would be around 37 degrees bc i know that's basically body temperature and Catalase in inside the body. 8. I'm just confused, does that mean the question is expecting us to apply some logic and know that the body temp is around 37?

I understand that the 80degree trial definitely caused the enzymes to be permanantly  denatured, as there was only 0.01cm of bubbles produced and there was no oxygen when we used the splint. 9. But what exactly would the ice water have done to the enzyme? I at first thought that cold temperatures just slow everything down. But after bathing the liver in ice water, we left it to go to room temperature, so wouldn't that speed things back up a little? 10. Or does the cold temperatures have a long lasting effect on the enzyme even after warming up to room temperature (which may have been higher than 20 degrees because it was a fairly warm day)? i should add, there was a reaction with the ice trial, it was slower than the room temp and 40 degree trial but it still seemed to be just as reactive as those two, but it slowed down quicker and reached a lower bubble height.
11. Basically, how does the cold temp effect the actual enzyme structure? or does it just slow it down. this one really confused me.

Half of this probs makes no sense. Sorry for the detail, i've never been good at being concise.
1) You're correct, because you changed them back to room temperature you were measuring how permanent the effect of temperature change was.

2) Yep, I would have done it your way. The reaction has stopped once the bubbles stop being produced.

3) It did not mean the enzyme was saturated - if it was saturated you would see a constant speed of reaction, the reaction would be occurring at its fastest rate possible so the bubbles would still be appearing, it would just not get faster.

4) It depends which tests were lower. If it was in the more extreme conditions then yes it could be due to some of the enzymes being denatured - or you could have just put slightly different amounts of hydrogen peroxide into your beakers.

5/6) Yep it would have meant that the reaction rate had either slowed to the point where you could no longer see an increase, or it had stopped. A decrease in hydrogen peroxide floating around would result in the rate of reaction decreasing so it is likely that at this point there was very little or no hydrogen peroxide left.

7/8) It depends on the question. If they want you to base the answer solely off your results they will normally say so (eg. 'state the optimal temperature with reference to your results'). The 40 degree one was cooled to room temperature, so when the reaction occurred they were no different. It is possible that some of the enzymes were denatured from the heating which would have slowed the reaction down.

9/10) Cooling enzymes down has no permanent effect once they have been heated up again, so the difference in results would mean that either it wasn't properly warmed back up or you made an error when making that beaker.

11) Cold temperatures mean less kinetic energy - everything moves slower. Molecules moving slower means they are less likely to bump into each other, and therefore that it is less likely for reactions to occur. It does nothing to the actual enzymes structure which is why it is not permanent. Only high temperatures have permanent effects (and extreme pH's in either direction).
Should my control group have white light or no light?
Hi guys. In an experiment investigating the effect of wavelength of light on the rate of photosynthesis, would the control group have no light or white light?
You would normally have both. The white light is a positive control, no light is a negative control.
Does my IV need to be on my X axis if I have more than 2 variables?
Does the independent variable in an experiment ALWAYS have to be on the horizontal axis? For example: let's say your measuring the rate of photosynthesis of a plant over time when exposed to different amounts of light. Can you put rate of photosynthesis on y axis, time on x axis and use different colored lines to indicate different amounts of light? Is there a better way to do this, cause I can't think of any other way you can graph 3 variables.
Hey, no the IV does not always have to be on the x axis. Rate of photosynthesis is your DV and that is on the Y axis so that’s correct.

I pulled out my prac on light colour that I did last year and I had put reaction rate on the y axis, time on the x axis and represented the different colours with different lines so you should be fine to do this for light intensity - I would check with your teacher though because they’re the one who is going to be marking it.

Your other option is to ignore time altogether (although this depends on how you are measuring the rate of reaction), the rate of reaction shouldn’t change much over time (although the amount of reaction will) so you could just use the average rate and put that on your y axis and then put light intensity on your x axis.

It would look something like this
In reverse though

Questions about how to write an EPI
Just have a couple of questions about the EPI:

1. In the results section, what can I comment on without doing too much explanation?

2. Where can I justify the use of oxygen gas production as a suitable dependent variable?

3. How can I comment on whether the investigation generated useful results?

4. How can I effectively comment on the meaning/significance of results obtained?

(1) Firstly, within the results section, comments or any descriptions are often unnecessary, merely data points and charts are adequate. I must mention, however, if your results have a qualitative component then laconic descriptions such as 'solutions altered from pink to blue' are sufficient etc.

(2) In terms of oxygen gas production acting as a dependent variable, justification throughout your poster is often implicit, that is, one doesn't often need to explicitly state that it is an appropriate dependent variable because... Rather, focus on identifying the process being observed in your introduction (i.e. photosynthesis), then briefly outline how it works (here you can acknowledge that oxygen is a product of the light-dependent reactions).

(3) In my opinion, this can be done in the discussion (in a far more detailed manner) or in the conclusion where it can be hastily stated and supported. (i.e. the findings of this investigation, in coinciding with current scientific theory, acts to bolster what is currently known, thus demonstrating the credibility of [insert aim of investigative research here etc].

(4) Lastly, when interpreting results (i.e. significance of results), this can be performed within the discussion where further drawings upon the data can be established and used to explain other scientific concepts etc.

Good luck :)

DISCLAIMER: I recommend you discuss these questions with your teacher when possible. My suggestions are merely my own opinion and due to the subjectivity of various schools' marking schemes for the Extended Practical Investigation, your teacher/(s) may expect different renditions of the poster to what I envisage.
What is meant by ‘design process in experiments’? How will it be applied to SACs?
"Design process in experiments"

What is this? And what do you need to know according to the study design? How is this gonna be applied to experimental SACs?

Thanks beforehand!
It basically just means that you need to know how to design an experiment. If you go to the study design and look at Unit 4 AOS 3 it has a list of everything you need to know. The main things are:
-Positive and/or negative controls
-Large sample size
-Repeat the experiment
-IV is valid
-You can measure your DV properly

For experimental SACs you'll likely be asked what the control/independent/dependent variables are or you'll be asked for ways to improve validity/reliability/accuracy (if you've covered this in class already, you may not have), or you could be asked how to improve an experiment (generally there will be an obvious mistake e.g. small sample size)
also worth adding to the above that it means you should be able to interpet the results of experiments and comment on how the method of the experiment could be improved. This is now a fairly important topic in all of science in VCE and isn't typically taught that well sadly!
What is the purpose of a control in an experiment?
what is the purpose of a control in an experiment?
The purpose of a control group is provide a basis of comparison of which to compare the effects of your experimental (independent) variable.
To ensure that the dependent variable isn't affected by any other factors other than the independent variable.
How should I write my method for my prac report?
Regarding the write up of an experiment, in a methodology how would you recommend writing out the steps in the method? Is it preferable to write out the steps in bullet points (e.g. - Place 3 algal balls in each test tube) or in past tense in a paragraph (e.g. 3 algal balls were placed in each test tube)? This may seem a little pedantic but I am quite curious as I would like to improve my expression in this area and my teacher hasn't given a definite answer.

Also, does a methodology usually contain a list of materials or just the method? If the method was written in past tense form would you still have to write out a separate list of the materials?

Thank you!
You are right, definitely do the method in past tense, for example:

1. 30ml of amylase stock solution and 15ml of starch solution were measured using two separate measuring cylinders and both were added into two separate 100ml beakers
2. The beaker containing amylase solution was  incubated at 30°C for 10 minutes
Etc etc

Methodology is a broad category of method (above) and materials (100ml beaker, 15ml starch solution), so you can have them separately.

You can improve expression for method questions by doing the Design an experiment questions from VCAA exams. An example of these types of questions include:

Design an experiment to test the hypothesis that increasing temperature of the lactase solution will increase the rate of lactose breakdown.
What is the baseline of an experiment?
2) What is the 'baseline' of an experiment in layman's terms? (2017 exam 11c)
2) I think baseline refers to the starting measurement for data. For example, in the first table of page 36 of q11 (2017 exam), you can see slight changes in % concentration and temperature from 0 minutes until 2 minutes. From 2 minutes to 4 minutes, it is the same -- and that is pretty much the baseline.
What’s the difference between accuracy, reliability, and precision?
3) What is the difference between experimental accuracy, reliability, and precision?
3) Accuracy refers to the difference between the experimental and true measurement obtained.

Reliability refers to the ability to obtain the same results if the experiment was repeated.

Precision refers to the agreement between values (how close values are) in each repetition of the experiment.
What’s the purpose of a control?
Also whats the purpose of a control?, for say a 2 mark question (according to VCAA exam reports)
I've heard varying responses from company notes, my teacher and online resources for this, not sure what to follow
The control is to give you something to compare your results to/give you a baseline for the experiment. Like if you were testing the effect of increased concentrations of carbon dioxide on plant growth, but all you had was one plant in a sealed container that contained higher than usual CO2, what would you compare that too? Just from that you can’t tell what affect the co2 has on it. Your control would be another plant in a sealed container with normal levels of co2, that way you can actually see what difference the increased co2 made.
What is meant by limitations in scientific method?
Anyone know what limitations mean? I'm doing a scientific method and it's asking for that
I believe that limitations of an experiment would simply refer to factors which cannot be controlled by the experimental setup but would still affect the results
To add to that, I would think that limitations may also be generally any disadvantages with an experimental design. This could include a experimental method that does not appropriately address the goal/research problem.
I suspect that it is also (although less) likely that limitations refer to the limits imposed by time, money, other resources such as the availability of a given material (eg. test tubes)
You've gotta be careful with this definition. It's the right idea, but a limitation isn't something that "can't be controlled"...the whole purpose of discussing them is to try to get rid of them, which is usually possible.

To understand limitations, you need to understand what an experiment is for. An experiment is to show that A causes B. That's all it does. Really good experiments demonstrate that connection in such a way as to eliminate any doubt that A caused B. Bad ones leave open a lot of questions. A limitation is anything that makes us doubt that A caused B, so yes, it can be variable that wasn't properly controlled. It can also be something inherent in the design of the experiment, too.
« Last Edit: February 27, 2019, 09:52:28 am by PhoenixxFire »
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Re: Biology Q&A archive/Bio FAQ
« Reply #18 on: February 27, 2019, 09:52:00 am »
Detailed answers/explanation for past exam/test questions
2009 U4 exam
With this VCAA question from the 2009 Exam 2 paper, could someone please explain how the answer is relevant to technological evolution? I thought it was to do with how changes in technology gave humans increased control over their environment - how is "information being passed on" relevant to it.. I thought it was cultural evolution? Thanks  :P

Q: The rate of technological evolution has been increased by the cultural evolution of Homo sapiens. Describe one example of the effect that cultural evolution has had on the rate of technological evolution.
A: Articulate speech/writing/painting/ceremonies enabled information to be passed on

tbh I find questions about the relationships between biological/cultural/technological evolution and how they influenced each other really confusing
Okay so what this question is really asking is for an example of cultural evolution that allows technological evolution to be fast. Technological evolution requires passing on the knowledge of how to make things so therefore Articulate speech/writing (an example of cultural evolution), which allows this to happen, is the answer.

MCQ about cystic fibrosis
Hey guys would someone be able to help me with this question? The correct answer is B btw:

The disease cystic fibrosis is caused by a gene mutation that produces an incorrectly formed protein channel, the CFTR (cystic fibrosis transmembrane conductance regulator). When this channel is not formed correctly, chloride ions will not be able to exit the cell. The accumulation of chloride ions causes the movement of water via osmosis.

Based on this information, which of the following are likely consequences of cystic fibrosis?

A. Large amounts of watery diarrhoea as chloride ions in the intestinal tract attract water.
B. Thick sticky mucus outside cells as water remains in the cell rather than move out via osmosis
C. Selective sodium channels provide an alternative passage of chloride ions.
D. Water will be actively transported into the cell following the accumulation of chloride ions.

I chose A as my answer because I thought that there would be a buildup of chloride ions inside the cell, meaning water would move into the cell via osmosis as the environment outside the cell would be hypotonic to the cell? Can someone explain why B is the correct answer instead? :P
Well you are quite right in saying that the water will move into the cell, as there would be a build up chloride ions in them. However, it is not A because the water moves into the cell where it would accumulate. For it to be A, the water has to move out of the cell into the intestinal tract, thereby causing diarrhoea.

Its not C, because a sodium channel is for sodium, so chloride would not be able to pass through
And can't be D, because water is never actively transported, if active transport is involved, then the movement of water always occurs through osmotic gradients created by the active pumping of ions

Therefore, because the water goes into the cell, then the extracellular environment wouldn't be as moist, so sticky mucus can develop
MCQ about fossil stratigraphy
I need help with this question

Excavations at a fossil site uncovered a layer of ancient fl ood debris. The layer consisted of stones and sand,
mixed with fossilised plant and animal remains. The debris had been deposited in a rocky river valley and then
covered with fi ne sandy sediment which was dated to approximately 10 million years ago.
In this situation it is true that
A. the fossils are less than 10 million years old.
B. the rocks of the valley walls are younger than the fossils.
C. the plants and animals lived in the same habitat.
D. the stones mixed with the fossils cannot be younger than the fossils

The answer is D but I don't know how you can reach that conclusion.
Simple, just imagine a dinosaur that fell into and died between a valley, and then sand comes and cover it, which then sediments into stone. So which one, the dinosaur or the stone do you think would be older? Remember than sand -> stone.
2015 Q7C
2015, Q7C
In the rat pituitary gland, GC stimulates the production of the growth hormone protein, However, in the rat liver, GC stimulates the production of the enzyme tryptophan oxygenase. Given that the genetic sequence is identical in all somatic rat cells, explain how the production of distinct proteins in different cell types could occur.

The answer is: Factors expressed by regulator genes could lead to the production of the different proteins

Could someone please explain what the factors expressed by regulator genes actually are? And would exon juggling/ alternative splicing be considered a valid answer?
I feel like the mean something similar to transcriptional factors. I emailed my teacher about this question too and she said that the old study design didn't have an emphasis on the stuff we do now. So, i think exon juggling could be considered a valid answer IMO. I think if it's reasonably justified and correct in terms of your knowledge, you should get the marks. The examiners reports don't list out all the potential solutions :)
Hi, so this question came up in the 2015 VCAA biology exam, and I was just wondering if somebody could explain why my answer is incorrect?

The question is (question 7c worth 2 marks)
In the rat pituitary gland, GC stimulates the production of the growth hormone protein. However, in the rat liver, GC stimulates the production of the enzyme tryptophan oxygenase.
Given that the genetic sequence is identical in all somatic rat cells, explain how the production of distinct proteins in different cell types could occur.

To answer this, I wrote (and please ignore the terrible wording...)
Alternative Splicing; what one cell produces as growth hormone and another as tryptophan oxygenase may differ as different codons are considered exons and introns in different cells, therefore coding for different amino acid sequences and consequently leading to the production of different proteins with different functions.

The suggested answer in the examiner's report says:
Factors expressed by regulator genes could lead to the production of the different proteins

Would alternative splicing not be a way that the production of distinct proteins in different cell types could happen?
This was actually discussed on here a few weeks ago, pretty sure your answer would be considered correct. In situations like this so long as your answer is reasonable and you've justified why it is correct then you should be fine. I reckon they might actually be referring to alternative splicing when they talk about 'factors expressed by regulator genes'.
As the above has stated the possible answers in the biology exam aren't always on the assesors report and many different answers can be accepted for some questions. From memory, the assessor gets a answer key with all the suggested answers however they can also use their own discretion to award marks if the student brings up something that is still correct and makes sense.
2017 SAQ 38
Could somebody please help me!!
This is my first time ever posting on here and I am so confused about this noe bio question.
So for the 2017 VCAA Bio exam, multiple choice questions 38 has got me so utterly baffled.
Could somebody please explain them to me. I have no idea what’s happening with this question and UGH so confused. Any help would be greatly appreciated :)

I’ve attached the question too BTW :)

Thank youuuuu
Hey, welcome to AN ;D

38. So this question is testing that you know how restriction enzymes and gel electrophoresis works.

So to start with, use row T. Row T only has two DNA fragments. In the answers table we can see that HaeIII, SaII, and BamI are the possible restriction enzymes that could have cut that fragment. Of those 3 restriction enzymes, HaeIII is the only one that has a single cut site drawn on the DNA strand above. This means that it is the only one that could have resulted in two DNA fragments (the rest would have resulted in 3). So now we know that the answer must be A or B

So then we use row U. Only options A or B on the table could have cut the DNA fragment. So it must be either BamH1 or Sall. Looking at the DNA fragment above, we can we that Sall would result in 1 short piece and 2 longer pieces, as seen on the gel electrophoresis in row U whereas Sall would result in two short pieces and one longer piece. Therefore it must have been Sall that cut this DNA fragment (option B). Therefore we now know that the answer is option B (you can also double check that option B also works for rows R and S).
2017 MCQ 39
Could somebody please help me!!
This is my first time ever posting on here and I am so confused about this noe bio question.
So for the 2017 VCAA Bio exam, multiple choice questions 39 has got me so utterly baffled.
Could somebody please explain them to me. I have no idea what’s happening with this question and UGH so confused. Any help would be greatly appreciated :)

I’ve attached the question too BTW :)

Thank youuuuu

(user asked for further clarification)
I think that probably means you're missing something about how either how gel electrophoresis works or how restriction enzymes work.

So for gel electrophoresis, it sorts DNA fragments by length. Shorter fragments travel faster. So they start at the 'wells' at one end (on the image they're a dark rectangle on the top). So you can guess fragments relative length by seeing how far they've travelled. Shorter fragments will have travelled further because they travel faster, so they'll be closer to the bottom of the gel electrophoresis on the image.

So we can then use that knowledge to determine the lengths of DNA fragments, for example in the line S there is one mark right at the top and two near the bottom - meaning that there is 1 long DNA fragment and two short DNA fragments.

The other part of figuring this out is knowing how restriction enzymes work. So a restriction enzyme will cut at a specific spot/s on a piece of DNA. The DNA molecule at the top of the page shows the spots where each of the restriction enzyme will cut, so if you are using EcoRI it will cut in 3 places, gicing you 4 DNA fragments.
(Image removed from quote.)

So then you know that the only line that could possibly be cut with EcoR1 is line R, because it's the only one that has 4 fragments.

So then you just have to figure out which restriction enzyme cut which of the other lines.

So EcoR1 cut DNA R, then you can figure out what BamH1 cut by using the length of the fragments

(Image removed from quote.)

(Image removed from quote.)

So now we can see that the only possible option would be B as it's the only one that matched the correct restriction enzyme with the correct DNA fragment (DNA piece U must have been cut by Saell because it's the only option left).
2017 MCQ 14
3.) Why is the Answer B for 2017 vcaa bio exam question 14 multi choice. I know it wasn't A and D, but why couldn't answer be C? Couldn't the light have saturated chlorophyll molecules?
3) It’s not saying the chlorophyll is saturated, it’s saying the chlorophyll is damaged. If it was damaged the net output would have gone down, this is not the case - as you can see in the diagram it has remained constant, therefore it can’t be C.
2017 MCQ 19
4.) Why is the answer D for 2017 vcaa bio exam question 19 multi choice. Couldn't answer be B? Why would D be more correct?
4) Decreased apoptosis in surrounding normal cells wouldn’t cause rapid division of cancer cells - the only option that would cause that is D.
2017 MCQ 40
2017 vcaa bio exam, question 40 multi choice. Why is answer B? How would you justify why other's are wrong?
Plant viruses are a major problem for farmers growing crops. A particular plant virus can infect many different plant species. Scientists are trialling a spray treatment on tobacco crops. The treatment does not alter the DNA of the tobacco plants. During this treatment, tobacco plants are sprayed with clay nanoparticles containing double-stranded RNA (dsRNA). The dsRNA released from each of the clay nanoparticles enters the plant cells. Inside each cell the dsRNA silences a gene from the virus by causing viral RNA to break down.
In this technique the
A. dsRNA would have a nucleotide sequence complementary to a section of DNA nucleotides in the tobacco plants. It is double stranded RNA which means it is already bound to complementary bases. Being complmentary to DNA nucleotides is irrelevant.
B. dsRNA would silence a gene from the virus by initiating changes that prevent translation of the viral gene. Given that the question states that the dsRNA acts on viral RNA, it makes sense that it would prevent translation.
C. spray treatment would be effective only on tobacco plants and not on other plant species. The question specifies that the virus affects many species, it is just happens to be tobacco plants that they’re trialling it on
D. sprayed tobacco plants would be regarded as transgenic organisms. The question specifies that it does not alter the plants DNA so the plants won’t be transgenic
2018 NHT MCQ 23
2018 vcaa bio northern hemisphere exam, question 23. Why is answer A?
23. A
The branching off lines represent a difference in evolution. The order they branch off in represents the order those characteristics evolved in. Archaea and bacteria don’t have mitochondria or chloroplasts so they branch off first (Everything on the 2 left branches has neither mitochondria or chloroplasts, everything on the right branch has mitochondria – indicated by the right branch being named ‘mitochondria’). Then fungi and animals split from plants (everything on the 2 left branches has mitochondria but not chloroplasts, the right branch is labelled ‘chloroplasts’ so everything on that branch (ie. plants) have chloroplasts).
2005 E2 Q5.b.
1. VCAA 2005 exam 2, question 5 b). little confused about this experiment. if there is growth of the fungus in tube 12, then how could the answer be that the fungus cannot produce histidine (the amino acid in tube 12)?
1. Histidine was added to tube 12. That's what they were testing. The fungus did not need to make its own histidine (because it was present in the tube) which meant the fungus could grow.
2017 MCQ 32
Can anyone explain how to interpret the phylogenic tree in the 2017 exam MCQ32? Thanks!
When I did this question I didn't really use the phylogenetic tree except for age. You don't need to use the info on the right to answer it. So from the tree you can see that the order from oldest to youngest is R-S-T-U (evolved first-evolved last).
So then you just have to look at the possible answers.
Which of the following shows the correct placement of the organisms on the phylogenetic tree?
A.     R – animals, S – plants, T – bacteria, U – protists
B.    R – bacteria, S – protists, T – plants, U – animals
C.    R – protists, S – animals, T – bacteria, U – plants
D.    R – plants, S – animals, T – bacteria, U – protists
Obviously neither animals or plants were the first to evolve, so we can strike out options A and D.
Animals evolved before bacteria, which means option C is incorrect. Leaving just the correct answer of option B.
2018 NHT SAQ1
So in the 2018 NHT VCAA exam, the first short answer question provides this information and asks:
Two students noticed bubbles forming on the submerged leaves of an Elodea plant growing in an
aquarium. The bubbles seen on the leaves were the result of a gas formed within the cells of the
leaves. The photograph below shows the appearance of these bubbles.
There was a bright light shining on the aquarium. The bright light was not affecting the temperature
of the water.
a. Describe what occurs within the cells of the leaves to result in the formation of these bubbles. (3 marks)

In my answer I talked about how it could be oxygen from photosynthesis or carbon dioxide from cellular respiration, however in the answers, it says:
Chlorophyll absorbs light energy, water is split to form hydrogen ions or oxygen gas, and oxygen
will diffuse out through the plasma membrane.

Is cellular respiration not also a potential cause of these bubbles?
It could be but given the question mentions leaves and light I’d say they wanted you to talk about photosynthesis.

Also likely that given the bright light, all the CO2 is being immediately used up in photosynthesis

Exam/study tips
How do you use reading time effectively?
How do you use reading time effectively? I try to answer multiple choice questions in my head because it helps me finish faster but I don’t know if this is a good strategy or not
You can do that, I found that it's possible to do maybe the first 10 -15  MCQs in reading time.  However, I chose to read through the SAQs more thoroughly because that is where most of your marks will come, they are the harder questions and the standard deviation between scores will be greater for SAQ than MCQ.
I read through the short answer in the reading time and then start from the multi choice once writing time starts.

I think this helped because I could start to think about the short answer questions before I got to them - that way I didn’t turn a page, see a hard question and start panicking. It also gave me an idea about what was coming up which helped with timing.

Try a few different strategies during practice exams and figure out what works for you.
My marks aren’t improving! Should I continue doing practice exams or revise another way?
So I'm doing 3/4 biology practise exams. I've done about 10 so far and I'm getting between 67%-75% constantly. I've been told that my scores will improve with the more that I do but they're not improving. Is this because I don't know the content well enough or should I keep doing practise exams and wait for the improvements to come along? I always fix up my mistake and correct the practise exams.
It depends on why you're getting questions wrong. Are you just writing the wrong thing? (like interpreting the question wrong, not giving enough information etc.) or do you not know the answer? If you haven't already then go back through them and keep track of what you're getting wrong - Are they all questions on the same topic/s? (My teacher gave us a table with each dot point of the study design printed into a different row and we put a mark next to the relevant part when we got a question on it wrong - it becomes obvious pretty quickly what you're messing up).

Potentially might be worth going back and redoing the same practice exams - see if your mark changes. If it doesn't then you need to change something (and if it does then great because you've learnt something since the first time you did it).

If you're getting 3/4 (or maybe 2) mark questions wrong then try writing out a few different full mark answers for it rather than just editing it to have a full mark answer. Writing out several different full mark answers (just worded differently or whatever) will force you to really think about it rather than just being like 'yeah i reckon I know that' and moving on. It'll make it way easier for you to remember it and find a way to easily answer it in future.

So yeah I reckon either:
-Keep a record of what you're getting wrong, if it's in the same areas then go over your notes/make summaries/etc for that area.
-Redo practice exams you've already done and see if your mark changes (or just redo all the questions you got wrong if you don't have time)
-Write out full mark answers in several different ways to help you remember it.
With the careless mistakes, grab a highlighter and as you go through highlight the important bits of the questions/things that you need to mention, it should help you quickly pick out the important bits amongst all the meaningless stuff that VCAA likes to put into questions. Also something I always did was reread the question after having answered it to make sure that I actually covered everything that I needed to.

When is it ideal to finish doing practice exams?
When is it ideal to finish up doing practice exams? I want to finish somewhat early, but I'm not sure how early is too early where you'd start to lose your mojo. If it means anything I'm currently intending to leave a couple of the company papers on the current design to do last, maybe on the weekend before the exam. I'm just not sure if that's the best way to pace myself.
I would probably be doing them up till a couple of days from the exam - from memory my Bio exam was on Friday and I think I did my last exam on Wednesday (and that was the most recent vcaa one at the time). They are quite long exams too so I wouldn't be doing one the day before.
What should I do in the last few days before the exam?
I am at the point where I can't think of any areas that I need to work on because I feel as though I know most of the stuff well, but whenever I do a practice exam i still am losing marks.
Does anyone have any suggestions for how to study in the last few days leading up the the exam?
I have done 17 practice exams, should I keep doing more or do something else?
still around 3 full days till the exam so i'd probably just do 1 exam to keep your routine going, it doesn't even have to be a full 2.5 hour exam (which is too long imo to be doing the day before your exam) you could just do a single unit exam - It's probably good to go over your past exams and see what you got wrong and why you go those questions wrong so that you don't make the same mistakes in the actual exam.
I’d suggest relaxing a bit tomorrow night (so don’t do a practice exam, just read over notes or write summaries or whatever) and then on Wednesday do another practice exam and completely focus on it and give it your best shot.

Given you think you know the content well, you’re probably losing marks on either misreading the question or not including enough detail? If that’s the case then go collect the questions you’ve gotten wrong recently and redo them rather than doing entire exams. But yeah, I reckon take it easy tomorrow night to relax a bit and then on Wednesday do another practice exam, it’s possible that whatever mistakes you’re making now are due to fatigue (not just lack of sleep fatigue, more so the fatigue that comes with constantly doing exams). If you don’t make as many mistakes after having taken a night off then you’ll know that’s why.
Maybe just read and write summaries again. I'm in the exact same situation as you and while I feel tempted to do practice exams, I feel like just reading and trying to take my time on questions help. Also studying with friends or doing a practice exam together helps get a sense of a thinking when doing questions. I find that the main problem is not fully understanding the question so maybe just break apart questions and figure out what it is  asking you.
What’s the best way to tackle comprehension questions?

What advice would you give for comprehension questions such as Short Answer Question 10 of the 2017 exam or Short Answer Question 10 of the sample exam ?
What is the best way to tackle such questions?

With questions with big chunks of information, I would quickly skim the info to get a basic idea of what it is about, read through all of the questions so that you know exactly what to look for, and then read through the information again and highlight, possibly in different colours (like for the one in the 2017 exam, you could highlight the parts that SUPPORT the rapid evolution model in one colour, and parts that DON'T support the rapid evolution model in another colour) - this will make the information easier to identify when answering the associated questions.
What’s the best way to use reading time?
what is the best way to use reading time?
For the reading time I read the short answer questions because it gives you a bit of an idea of what's ahead - you know whether you're going to turn the page and have 1 question or 6 questions - and then I start from the multi choice during writing time.
What should I do for last minute revision?
What is everyone doing as last minute revision? I don't know what to do
I went over the study design as a checklist, looked over my errors in practice exams, and am currently asking/answering questions. And then after that, I guess I'll have a panic attack or breakdown (or a few) later today  :)
Is it worth writing notes according to the study design?
I have a question that is not necessary theory related but more specific to the biology course. I'm wondering whether it is worth writing notes according to the study design, that is, with the headings being the dot points in the SD. Anyone know if this is a good way of doing it? Thanks in advance  :)
I am going to give you an answer you probably won't like, but it really depends on what works for you as to how you make notes. Personally I didn't make notes under each study design point and followed a more 'topic' based structure as is that of a textbook. I'm sure though that others have done differently and been sucsessfull with it. I think it's all about what you find comfortable.
If you asked me though, I would say that making notes under study design points would serve me better as a revision tool than for preliminary learning.
Hope my rambling here may offer some help, and good luck with biology  :)
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Re: Biology Q&A archive/Bio FAQ
« Reply #19 on: February 27, 2019, 10:05:57 am »
Incredible work, PF!

Almost 5,000 views for this thread so far, and a lot of gratitude!