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Author Topic: VCE Biology Question Thread  (Read 3570942 times)  Share 

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rainbowsparkles15

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Re: VCE Biology Question Thread
« Reply #9330 on: October 01, 2017, 03:21:09 pm »
+1

Hey all,

I know that T Helper cells stimulate the B cells to differentiate, do they also do this to T cells?
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LifeisaConstantStruggle

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Re: VCE Biology Question Thread
« Reply #9331 on: October 01, 2017, 03:27:37 pm »
+2
Hey all,

I know that T Helper cells stimulate the B cells to differentiate, do they also do this to T cells?

Yeah they do it to Tc cells as well, and T memory cells are also produced (a question on these cells was actually in one of the *spoilers* vcaa exams so yeah)
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rainbowsparkles15

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Re: VCE Biology Question Thread
« Reply #9332 on: October 01, 2017, 03:31:51 pm »
+1
"Significant changes in life forms in Earth's geological history including the rise of multicellular organisms, animals on land, the first flowering plants and mammals"

for this dot point in the study design, what exactly is it that we're expected to know?
do we just need to know the eras (from the geological time scale) in which each of these things happen and then a description of sorts of what the organisms may have looked like/lived like??

I was really unsure of this point myself! My teacher didn't spend any time on it at all....
To be safe, I'm planning on learning when each of the events occurred and a brief description of how they came about/ what they did etc. so similar to your thoughts

Sorry I can't provide an answer that's more certain, tough being the first year for the new course
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Agentbarks

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Re: VCE Biology Question Thread
« Reply #9333 on: October 01, 2017, 06:48:57 pm »
+1
In smaller populations, each individual makes up a higher proportion of all the alleles than in larger populations. In large populations, chance events (such as an individual dying) don't really affect the allele frequency. In smaller populations however, the death of one individual can drastically change the allele frequency. Suppose I had a population in which  50% had genotype RR and the other 50% had genotype rr. In a population of 1000, if one individual were to die, the relative frequency would still be around 50/50. In a population of 2 however, if one individual were to die, then one of the genotypes just gets removed.
I hope this makes sense

Makes perfect sense, thank you so much :)

Apricot

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Re: VCE Biology Question Thread
« Reply #9334 on: October 02, 2017, 11:50:14 am »
+1
Can I please have some help with a few questions I have?
1) How can carbon dating be used to date actual fossils if the fossils are replaced by minerals through the process of mineralisation?
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?
3) When defining MRNA, should we mention that "MRNA carries a copy of a segment of genetic code of DNA from nucleus to ribosome" or just mention that it "carries a copy of a segment of genetic code of DNA to the ribosome," VCAA definition in one exam mentioned nucleus but I was thinking that bacteria don't have a nucleus yet they still do transcription involving MRNA?
4) Do naive B cells and T helper cells only recognize their specific antigens in lymph nodes, or is it other locations too?
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?
6) If we were asked on how to transfer genes between Eukaryotic organisms (to make GMO animals), would we talk about viral vectors and liposomes or are there other techniques?
7) How would an antibiotic be introduced into GMO's? The Nature of Biology textbook says this can occur but not sure how?

Sorry for the plethora of questions but it would be really appreciated if someone could help, thank you

rainbowsparkles15

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Re: VCE Biology Question Thread
« Reply #9335 on: October 02, 2017, 12:31:10 pm »
+4
Can I please have some help with a few questions I have?
1) How can carbon dating be used to date actual fossils if the fossils are replaced by minerals through the process of mineralisation?
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?
3) When defining MRNA, should we mention that "MRNA carries a copy of a segment of genetic code of DNA from nucleus to ribosome" or just mention that it "carries a copy of a segment of genetic code of DNA to the ribosome," VCAA definition in one exam mentioned nucleus but I was thinking that bacteria don't have a nucleus yet they still do transcription involving MRNA?
4) Do naive B cells and T helper cells only recognize their specific antigens in lymph nodes, or is it other locations too?
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?
6) If we were asked on how to transfer genes between Eukaryotic organisms (to make GMO animals), would we talk about viral vectors and liposomes or are there other techniques?
7) How would an antibiotic be introduced into GMO's? The Nature of Biology textbook says this can occur but not sure how?

Sorry for the plethora of questions but it would be really appreciated if someone could help, thank you

Great questions! (I would try and provide an educated guess to most of them but think its better if someone who is certain answers them!)

For question 2, I think this refers to the suspected interbreeding between the two groups. 'New alleles' would have been introduced into the gene pool. By this I mean alleles that weren't present in that particular population may have entered when they interbred. This then means that there are new alleles that can be passed down to future generations and changes the allele frequencies of the population. (Note these alleles have not been 'created' they are simply passed along when interbreeding occurs)

For question 5, repeating an experiment (with all the same controlled variables) will not reduce the effect of a systematic error as a systematic error is a consistent error such as a scale (or measuring cylinder, stopwatch etc.) that is calibrated slightly incorrect. If the same scale was used every time the experiment was repeated (which it should be) then the mistake in mass will be the same regardless of how many times the experiment is repeated.

Sorry I can't be of more help, if there are flaws in my answers please correct me !
« Last Edit: October 02, 2017, 12:42:43 pm by rainbowsparkles15 »
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PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #9336 on: October 02, 2017, 12:34:57 pm »
+10
1) Carbon dating can only be used on very new fossils (not 'true' fossils) that still have carbon which is why it is not particularly useful.

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.

3) It would depend on how the question is worded. In VCAA exams I doubt they would just ask you to define it without context. If your context has a nucleus then mention it if they're talking about a bacteria then don't. In bacteria its sort of like the ribosomes find the mRNA not so much the other way around. It can end up being translated whilst it is still attached to the DNA and being transcribed - This is why bacterial DNA doesn't have introns.

4) They don't only recognise them in lymph nodes, they recognise them whenever they happen to bump into them (ie. in the blood or lymph) but most naive B and T cells are in lymph nodes at any point in time. Think about it like a fish swimming around trying to find another particular fish - They could find each other in a river but they are far more likely to find each other in the ocean.

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.

6) I don't know about this maybe someone else can knows? I need to revise this myself lol.

7) Do you mean like the gene for antibiotic resistance? Or an antibiotic to kill it?
For resistance it would be the same as they introduce any other gene. If they wanted to see which bacteria could survive antibiotics (eg. to see which had successfully gotten the resistance gene) then I guess they'd just dump the antibiotic on top of them? I don't know exactly how but I don't think we need to know that.

Feel free to ask any other questions you come up with or let me know if this doesn't make sense.
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areeb008

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Re: VCE Biology Question Thread
« Reply #9337 on: October 02, 2017, 01:05:12 pm »
+1
Just with signal transduction, is the effector the molecule that acts as a transcription factor and alters gene expression, or the protein that is produced as a result of it that has an effect on the cell? Thanks in advance!!

PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #9338 on: October 02, 2017, 01:19:10 pm »
+6
It would depend on the context of the question. If you start with a signalling molecule then the response would be a protein being produced which would make the transcription factor the effector because it carries out the response.

However if you start with the transcription factor being a stimulus for a response eg. lowering blood glucose levels then Insulin (the protein produced) is the effector because it carries out the response.

So it really depends on what your initial stimulus and your response are. Was it a particular question you were having trouble with or just a general query?
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LifeisaConstantStruggle

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Re: VCE Biology Question Thread
« Reply #9339 on: October 02, 2017, 01:30:13 pm »
+1
It would depend on the context of the question. If you start with a signalling molecule then the response would be a protein being produced which would make the transcription factor the effector because it carries out the response.

However if you start with the transcription factor being a stimulus for a response eg. lowering blood glucose levels then Insulin (the protein produced) is the effector because it carries out the response.

So it really depends on what your initial stimulus and your response are. Was it a particular question you were having trouble with or just a general query?

But if the transcription factor turns a gene on, wouldn't the molecule produced after the expression of the structural gene be the effector instead?
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PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #9340 on: October 02, 2017, 01:43:05 pm »
+9
That's why it depends on the context if the question gives you the information

1) Signalling molecule binds to receptor (lets say it's a signalling molecule that will increase the rate of transcription of insulin), you know its going to act as a transcription factor and it asks
What is the cellular response?

The response is to increase production of insulin. Therefore the effector is the thing that makes it increase the rate of production ie. the transcription factor.

However if you know that the response is a decrease in blood sugar levels then the effector will be the insulin as that is what causes the response.

If you have any questions asking about this they will make it easier to explain as its kind of hard without a scenario. Easiest way to think about it is that the effector carriers out the response. That's why your effector will always depend on what the scenario says the response is.


eg. using your example of saying that the product of the gene is the effector, what if that product was insulin. So Insulin is your effector, It carries out the response of lowering blood glucose, correct? But then the lowering of blood glucose causes a person to not have a heart attack that is also a response true? The lowering of blood glucose is the effector in stopping a person having a heart attack. It just goes on and on. You really need to know the response or at least the scenario to decide what the effector is.

EDIT: Typo
« Last Edit: October 02, 2017, 01:45:01 pm by PhoenixxFire »
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rainbowsparkles15

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Re: VCE Biology Question Thread
« Reply #9341 on: October 02, 2017, 02:28:54 pm »
+1
A few questions,

Regarding monoclonal antibodies, do you think we need to focus on how they are produced or more the ways in which they target cancer (deliver chemotherapy to tumours etc.)

Which period did the rise of mammals occur in?  (I've seen a few different times in different resources)

Do we need to understand how messages are transferred across neurons as part of signal transduction? (action potential etc.)
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PhoenixxFire

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Re: VCE Biology Question Thread
« Reply #9342 on: October 02, 2017, 02:48:50 pm »
+9
Monoclonal antibodies: I don't think we need to know much about monoclonal antibodies as it is a very small dot point. I'm just planning on revising both but not in great detail.

Mammals:
I really need to revise the evolution timeline so can't help much with that, from my understanding the dinosaurs were wiped out and then giant mammals evolved as a result of the lack of competition, then due to too many resources being used (big animals need more food than small animals) etc. they evolved to be smaller (aka current mammals)

Neurotransmitters: My teacher taught a few of us how it happens at a lunch time so I get the impression you don't need to know it. It isn't outlined on the study design specifically, neurotransmitters are just mentioned as a signalling molecule.

I would say that you only need to know that an electrical impulse (action potential) reaches the end of a pre-synaptic neuron, causing vesicles in the end of the neuron (axon terminal) containing a neurotransmitter to degranulate (release their contents) into the synaptic gap. The neurotransmitter diffuses across the synapse and binds to a (highly specific) ligand-gated channel protein, causing the channel protein to open, allowing ions to enter which causes an electrical impulse in the post-synaptic neuron (or target gland, muscle), the process repeats until it reaches its target tissue.

EDIT: Clarity
« Last Edit: October 02, 2017, 02:50:47 pm by PhoenixxFire »
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Apricot

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Re: VCE Biology Question Thread
« Reply #9343 on: October 02, 2017, 03:01:01 pm »
0
Great questions! (I would try and provide an educated guess to most of them but think its better if someone who is certain answers them!)

For question 2, I think this refers to the suspected interbreeding between the two groups. 'New alleles' would have been introduced into the gene pool. By this I mean alleles that weren't present in that particular population may have entered when they interbred. This then means that there are new alleles that can be passed down to future generations and changes the allele frequencies of the population. (Note these alleles have not been 'created' they are simply passed along when interbreeding occurs)

For question 5, repeating an experiment (with all the same controlled variables) will not reduce the effect of a systematic error as a systematic error is a consistent error such as a scale (or measuring cylinder, stopwatch etc.) that is calibrated slightly incorrect. If the same scale was used every time the experiment was repeated (which it should be) then the mistake in mass will be the same regardless of how many times the experiment is repeated.

Sorry I can't be of more help, if there are flaws in my answers please correct me !

For question 5, I confused systematic with random error, so will repetition reduce the effect that random errors in trials have on the results, as well as uncontrolled variables?

But thank you for your help!

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Re: VCE Biology Question Thread
« Reply #9344 on: October 02, 2017, 03:07:43 pm »
+6
It will reduce the effect of random errors as they only occur in one repetition of the experiment. So they will then be averaged out with other correct results. Repetition will help any uncontrolled variables that are only present in SOME of the repetitions. If uncontrolled variables have the same effect in ALL of the experiments then repetition will not help (as you are just averaging many incorrect results).
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