VCE Biology Question Thread

[salma.yaqoobi]

Hey! Definitely don't delete any of your previous posts - I'm certainly not going to transfer any existing threads here. Let's keep this thread for whatever questions may arise from now

[salma.yaqoobi]

Why is pedigree analysis often the easiest way to investigate inheritance patterns in humans?

[vox nihili]

Why is pedigree analysis often the easiest way to investigate inheritance patterns in humans?

What do you think? You're not going to get much from the forum if you just copy paste your homework without giving it a crack yourself.

[maheenkhan]

Hi!
I was wondering if I could get feedback on a Biozone question about PCR.

Question:
Describe how the polymerase chain reaction works.
Answer:
Denaturation- A DNA sample is denaturated by heating to 95 degrees, hence breaking the hydrogen bonds and separating the DNA into single strands
Annealing- The sample is cooled to 95 degrees and primers are added, which bind to complementary sequences on the target DNA at alternating positions
Extension- The sample is heated to 72 degrees so that Taq polymerase uses free nucleotides to extend the primers and synthesise complementary strands of DNA.

[Sine]

Hi!
I was wondering if I could get feedback on a Biozone question about PCR.

Question:
Describe how the polymerase chain reaction works.
Answer:
Denaturation- A DNA sample is denaturated by heating to 95 degrees, hence breaking the hydrogen bonds and separating the DNA into single strands
Annealing- The sample is cooled to 95 degrees and primers are added, which bind to complementary sequences on the target DNA at alternating positions
Extension- The sample is heated to 72 degrees so that Taq polymerase uses free nucleotides to extend the primers and synthesise complementary strands of DNA.

Good explanation however there are a few improvements to be made.

When you say "cool to 95 degrees" in the second step that should be to 55-60 (although this may just be a typo on your part).
Also, make sure to include the 4th step of PCR which is to repeat the process many times until enough DNA is produced.
You could also add in the direction that nucleotides are added if you want.

[Rameen]

Hi
Do smaller DNA fragments move faster in gel electrophoresis because they have a larger surface area and less resistance that enables them to travel through the porous agar faster?

[Sine]

Hi
Do smaller DNA fragments move faster in gel electrophoresis because they have a larger surface area and less resistance that enables them to travel through the porous agar faster?

Pretty close, the surface area is hard to say since you don' know the conformation of the DNA
I would say smaller fragments of DNA move faster as they are far less impeded in their movement than larger fragments whilst moving through the porous agar. (basically they can get through the gel more easily due to their size).

[Chocolatemilkshake]

Hey everyone,

I'm unsure whether I am fully correct about my understanding of the BMP4 gene. If you don't mind, I've condensed my understanding (from a number of resources) below and it would be great if I could have someone check to make sure it's correct.

- BMP4 binds to the surface of cells stimulating them to divide/differentiate (by altering expression of genes involved in division and differentiation.) The amount of BMP4 present at different developmental times of the organisms will lead to different expression of these genes.
- Thus, the mutations that cause different differentiation/cell division (leading to notable phenotypic traits) are within the regulator genes that regulate the expression of BMP4.

Also I've been posting a lot of question lately, so thanks so much for all your help again  !!!!

[vox nihili]

Hey everyone,

I'm unsure whether I am fully correct about my understanding of the BMP4 gene. If you don't mind, I've condensed my understanding (from a number of resources) below and it would be great if I could have someone check to make sure it's correct.

- BMP4 binds to the surface of cells stimulating them to divide/differentiate (by altering expression of genes involved in division and differentiation.) The amount of BMP4 present at different developmental times of the organisms will lead to different expression of these genes.
- Thus, the mutations that cause different differentiation/cell division (leading to notable phenotypic traits) are within the regulator genes that regulate the expression of BMP4.

Also I've been posting a lot of question lately, so thanks so much for all your help again  !!!!

Just want to acknowledge first that this is a really good way to ask a question and will likely mean that you're getting a lot more out of AN than people who just regurgitate their homework.


You're on the right track with your explanation, but for mine at least, there's a little bit of a gap between your first and second statement. Why does what you've said mean that mutations that affect BMP4 expression have an impact?

[Chocolatemilkshake]

Just want to acknowledge first that this is a really good way to ask a question and will likely mean that you're getting a lot more out of AN than people who just regurgitate their homework.


You're on the right track with your explanation, but for mine at least, there's a little bit of a gap between your first and second statement. Why does what you've said mean that mutations that affect BMP4 expression have an impact?

Sorry if that didn't make sense. My thinking here was that...

1. It is the amount of BMP4 protein present during stages of development that affect the phenotype of the organism, not changes in the BMP4 protein itself.
2. Therefore, the "chance events within genomes (study design)" or mutations that cause different phenotypes would not be within the BMP4 gene that produces the protein, but the regulator genes that control how much the BMP4 gene undergoes translation. (as it is the amount of BMP4 protein present not a direct change in the protein that affects the phenotypes - "galapagos finches and jaw formation of cichlid fish").

Hope that kinda clears up what I was trying to say, is this understanding incorrect? Perhaps this is not necessary to know, I'm still a little unsure. As always, thanks for your help!

[Comet striker]

Hello AN biology o/ ,
Im here back to ask questions because Im paranoid about wording. I have a ton of questions to be addressed. Fun times
Lets start with DNA hybridisation, heres what I know, you guys help with if its unclear and what I could add on:
- DNA is isolated from two species of interest.
- DNA is then heated to 95*C(also important question. Whats the temperature? Pearson's book says 95*C) to break hydrogen bonds between strands.
- Isolate one strand from each species and mix them together( is the word 'mix' the best term to be used?)
- Cool the DNA until the strands reform hydrogen bonds with complementary bases.
- Reheat the DNA till all hydrogen bonds between strands are broken again and measure the temperature required to do so.
High temperature = more related , Low temperature = less related

How do fossils form? (Fossilisation )
From my understanding:
- Death of organism
- Tissues and other soft body parts decay/decompose
- Sediments accumulate over the body preserving hard bodied parts.

What is natural selection? (Kinda looking for the perfect 1 line definition but idk if its possible lol)
Natural selection is the process by which the environment directly acts on the phenotype of organisms often choosing the most fittest in its environment and allowing it to pass on its traits.

Positives of selective breeding:
I have one. I need 2/3.
- Selective breeding chooses for animals that are the most beneficial for humans and thus increase the efficiency of products.
Quick google search gives u
- It can create new varieties of good crops. : Isnt this the exact opposite? Since companies normally opt for crops that are similar and dont like variety?
- It helps eliminate diseases. : Idk about this, since selective breeding doesnt choose for the fittest organism and better immunity isnt really whats invested in. Companies also normally use antibiotics too sooo idk.
Rest feel like they say the same thing. Also this is the first seach that comes up so didnt look that deep lol
Last one. Check wording and if I mentioned everything lol.
Why are frameshift mutations so dangerous
Frameshift mutations involve the addition/ deletion of a base rather than substitution. This results in changes to every codon after the mutation site as DNA is degenerate.
~Thnx o>

[vox nihili]

Sorry if that didn't make sense. My thinking here was that...

1. It is the amount of BMP4 protein present during stages of development that affect the phenotype of the organism, not changes in the BMP4 protein itself.
2. Therefore, the "chance events within genomes (study design)" or mutations that cause different phenotypes would not be within the BMP4 gene that produces the protein, but the regulator genes that control how much the BMP4 gene undergoes translation. (as it is the amount of BMP4 protein present not a direct change in the protein that affects the phenotypes - "galapagos finches and jaw formation of cichlid fish").

Hope that kinda clears up what I was trying to say, is this understanding incorrect? Perhaps this is not necessary to know, I'm still a little unsure. As always, thanks for your help!

Smashed it

[xxxjss]

Hello AN biology o/ , Im here back to ask questions because Im paranoid about wording. I have a ton of questions to be addressed. Fun times

1. Overall DNA hybridisation seems g, I was taught to mention at the beginning that the DNA obtained was purified and cut into fragments ( idk if this is redundant tho ) and temperatures around 95C would do the trick for breaking hydrogen bonds as with PCR it is ~95 to denature DNA.

2. I would throw in that the deceased organism is rapidly buried

3. My 'basic' definition for natural selection is where the most favourable/fittest phenotype to a certain environment has a greater chance at surviving and reproducing than others... not gon lie defining natural selection is a toughie and I'm not certain I've captured the full essence of what it needs to be

4. Selective breeding does have the possibility to remove unwanted or adverse alleles out of a certain population. This could include a genetic disease, so it sort of can eliminate disease (just that the process of selective breeding also increases the susceptibility to other diseases and ya know random mutations can do their thing ). So, whilst selective breeding does not choose the fittest organism, humans can still choose what they deem the healthiest and ones that lack genes for diseases. It even could be breeding two organisms that have resistance to disease, hence increasing resistant allele and bam bye bye disease for that growing population

5. I don't think you've answered the question quite right; it asked why it is dangerous and you have just defined what frameshift mutation is. I think its dangerous because of the subsequent nucleotide changes from the mutation, the incorrect amino acids are translated, producing a dysfunctional protein that varies dramatically to the intended one. Wrong protein = unable to do job = body suffers and complications arise

Hope this helps  feel free to question my answers too, I am a mere student 

[Comet striker]

1. Overall DNA hybridisation seems g, I was taught to mention at the beginning that the DNA obtained was purified and cut into fragments ( idk if this is redundant tho ) and temperatures around 95C would do the trick for breaking hydrogen bonds as with PCR it is ~95 to denature DNA.

2. I would throw in that the deceased organism is rapidly buried

3. My 'basic' definition for natural selection is where the most favourable/fittest phenotype to a certain environment has a greater chance at surviving and reproducing than others... not gon lie defining natural selection is a toughie and I'm not certain I've captured the full essence of what it needs to be

4. Selective breeding does have the possibility to remove unwanted or adverse alleles out of a certain population. This could include a genetic disease, so it sort of can eliminate disease (just that the process of selective breeding also increases the susceptibility to other diseases and ya know random mutations can do their thing ). So, whilst selective breeding does not choose the fittest organism, humans can still choose what they deem the healthiest and ones that lack genes for diseases. It even could be breeding two organisms that have resistance to disease, hence increasing resistant allele and bam bye bye disease for that growing population

5. I don't think you've answered the question quite right; it asked why it is dangerous and you have just defined what frameshift mutation is. I think its dangerous because of the subsequent nucleotide changes from the mutation, the incorrect amino acids are translated, producing a dysfunctional protein that varies dramatically to the intended one. Wrong protein = unable to do job = body suffers and complications arise

Hope this helps  feel free to question my answers too, I am a mere student 

Thnx this helps me a lot o>

[forsande]

Hey guys,
I just got my sac back and one of the question was this (this was 2 marks):

"What causes mast cells to overreact and cause an allergic reaction?"

My answer was: Mast cells have igE antibodies embedded (teacher wrote that ige binds to mast cells rather than embed) on it's surface. Normally, an allergic reaction occurs when something small, like a pollen, binds to two or more igE antigen binding site, but people with allergies have mast cells with many igE, so there's a higher chance for pollen to cross-link more antibodies which causes mast cells to produce a chemical called histamines that binds to walls of capillaries to dilate blood vessels and increase permeability of vessels. (Lol I know I kinda overwrote it, but my teacher is highly pedantic so I wanted to make sure I covered every point.)

I didn't get any marks, and my teacher wrote that 'I had the key points of including mast cells, igE and allergerns + mentioning cross-linking, but my concept was wrong' - I can not see how I'm wrong, or how I couldn't even get half a mark, any help please?