VCE Biology Question Thread

[Larz_acccccccccccccccccccccc]

Do we need to know about polymorphism?
thanks

[PhoenixxFire]

Do we need to know about polymorphism?
thanks

Polymorphism is a very broad term that just means that there's more than one phenotype present in a population. It's not really any different to saying that there's multiple phenotypes present, so you do need to know that content, but I doubt you need to know that word for it.

[xenx]

1) I am not aware of VCAA saying T cells differentiate to give rise to Helper t cell, cytotoxic T cells - do you know what exams mentioned this?. I have found them defining that "T memory cells survive for many years and proliferate rapidly into Th and Tc cells when the body is exposed to a pathogen for the second time, mounting a quicker and stronger response".
Helper T cells will differentiate to produce more helper T cells and memory helper T cells, but VCAA doesn't seem to want you to make the distinction between the two types of memory T cells, and instead wants you to group them as 'T memory cells'.

2)Antibodies are still effective against viruses. The humoral immune system may be activated by viral antigens and antibodies specific to these viral antigens can be produced where they will bind to the virus itself function to:
 - neutralise the virus (i.e. by antibody binding to a surface protein (of the virus) which enables the virus to bind to host cells, thus preventing the virus from binding to host cells and replicating).
 - Agglutinate virus particles, preventing their movement through the body
 - act as an opsonin and enhance phagocytosis of the virus

3) I would agree with this response

4) NK cells do release perforin and granzymes. NK cells do play a role in tissue rejection - but I think most questions will want you to talk about cytotoxic T cells.

5) This question is a bit odd - was there more context that came with it?

Thanks for the help! Here the context for the question:
qat 2018 sa 5
When a tattoo is performed, pigments that make up the ink are injected into the skin. New research has investigated the role of macrophages in tattoos. When the wound is created as a result of the skin being punctured, macrophages are present at the site of the wound. The research has found that the macrophages move to the site where they capture the pigment and remain there until they die. They become trapped, due to the size of the pigment, and the pigment is then released. This creates a cycle, that is continually repeated when another macrophage then arrives to take up the pigment and subsequently dies. Prior to this research, it was thought that dermal cells in the skin had permanently trapped the pigment.

also, with the inflammatory response, does mast cells in the injured cells release histamines which cause inflammation, vasodilation and increased permeability of the blood vessels, allowing phagocytes to arrive at the site of infection faster. And then the phagocytes that release cytokines which attracts more phagocytes to the site of infection.
 
 

[radiant roses]

I have a question from Question 9c of VCAA 2017 Exam
The exam report only says:
"Grow the bacteria on agar containing ampicillin.
Those bacteria that will grow on agar containing ampicillin have the plasmid with the human gene
included.
If plasmid is not taken up, those bacteria are killed by ampicillin."

It doesn't say anything about tetracycline, which was the other antibiotic resistance gene used in the plasmid.
Would my response be correct if I included:
- successfully transformed bacterial cells will be sensitive to, and not grow in presence of, tetracycline because the tcl gene was interrupted when gene of human protein was inserted into plasmid
- transformed bacteria will grow in presence of ampicillin because this gene is able to be expressed
- is plasmid is not taken up, bacteria are killed by ampicillin

[Sine]

I have a question from Question 9c of VCAA 2017 Exam
The exam report only says:
"Grow the bacteria on agar containing ampicillin.
Those bacteria that will grow on agar containing ampicillin have the plasmid with the human gene
included.
If plasmid is not taken up, those bacteria are killed by ampicillin."

It doesn't say anything about tetracycline, which was the other antibiotic resistance gene used in the plasmid.
Would my response be correct if I included:
- successfully transformed bacterial cells will be sensitive to, and not grow in presence of, tetracycline because the tcl gene was interrupted when gene of human protein was inserted into plasmid
- transformed bacteria will grow in presence of ampicillin because this gene is able to be expressed
- is plasmid is not taken up, bacteria are killed by ampicillin

I think you have the right idea of what is going on but your answer could be better linked together. I would probably give your answer a 2/3.
1 mark for the first two lines and 1 mark for the last line.

To get the third mark you need to explicitly state your procedure and talk about what would happen for the bacteria that did not obtain the plasmid (will they grow/not grow under certain conditions)

E.g. "A scientist would grow the bacteria on an agar plate containing ampicillin/tetracycline" then go onto to talk about whether you expect them to grow or not as you have.

[PhoenixxFire]

- successfully transformed bacterial cells will be sensitive to, and not grow in presence of, tetracycline because the tcl gene was interrupted when gene of human protein was inserted into plasmid

The question stem seems to imply (although not very well) that every plasmid has taken up the human gene which would mean that every bacteria cell would die in tetracycline either because of not having a plasmid or because of having an interrupted tcl gene.

[WhatisaMeMe]

Hi.

If the cell does not pass the checkpoints G1,G2,M, the cell goes into G0. But does DNA repair through enzymes such as dna ligase and base excision repair enzyme occur here in g0 or the cell cycle phases. Also, does apoptosis occur when the cell goes into g0 or not. Thanks.

[215072]

Hi i need help on transcription and translation in simple terms

[IThinkIFailed]

Hi i need help on transcription and translation in simple terms

Transcription:
DNA unwinds, RNA polymerase binds to promoter sequence, then transcribes template strand, constructing a complementary mRNA strand. Once it reaches a terminator sequence, this pre-mRNA is released.

Translation-
The mRNA leaves the nucleus, then binds to the ribosome. Once it reaches a start codon, translation starts and tRNA molecules carry specific amino acids from the cytosol to the ribosome, then bind to an mRNA codon complementary for its anticodon sequence. The specific amino acid then joins the growing polypeptide chain via condensation polymerisation.

[IDefinitelyFailed]

Wow, here’s a 50 SS guy, thanks so much...
Anyways, I know a guy who said he wasn’t studying after 10??

[Comet striker]

Hello AN,
Have a few multiple choice question clarifications while I prep for the finals days before exam.
1) One of the main roles for cells of the ovaries and testies is to synthesis the hydrophobic cholesterol based hormones oestrogen and testosterone respectively. Given the function, the most abundant organelle in these cells would be:
I went for Rough endoplasmic reticulum, while the answer states smooth endoplasmic reticulum. Can anyone help me on this? from my understanding rER produces proteins for export while sER produces proteins for use within the cell. Since both are hormones I assumed they would be exported.

[Bri MT]

Hello AN,
Have a few multiple choice question clarifications while I prep for the finals days before exam.
1) One of the main roles for cells of the ovaries and testies is to synthesis the hydrophobic cholesterol based hormones oestrogen and testosterone respectively. Given the function, the most abundant organelle in these cells would be:
I went for Rough endoplasmic reticulum, while the answer states smooth endoplasmic reticulum. Can anyone help me on this? from my understanding rER produces proteins for export while sER produces proteins for use within the cell. Since both are hormones I assumed they would be exported.

The clue in this question is "hydrophobic" this tells us that these are lipids, and thus that the sER will be responsible.

[Comet striker]

The clue in this question is "hydrophobic" this tells us that these are lipids, and thus that the sER will be responsible.

Ahh learn more everyday. I'm getting stuff mixed. sER synthesis lipids. Free ribosomes produce proteins for cells to use.
- also from the vcaa 2018 exam 1b:
My chosen organelles was  rough Endoplasmic reticulum, Golgi apparatus and mitochondria. The report says vesicles is also an option. Are vesicles considered an organelle?
- Also what are the specifics in terms of cultural evolution of each hominin species do we need to know? For eg do we need to know homo erectus was the first to discover fire.

- Also while we are on the topic, what do we need to know about Australopithecus genus(I think its a genus idk lmao). How do they relate Homo?

- I also kinda keep messing up on what can pass through the plasma membrane, any good tips on how to remember what can pass through? especially when determining whether a molecule is small enough to pass through or not. 
Thnx for the help

[PhoenixxFire]

Ahh learn more everyday. I'm getting stuff mixed. sER synthesis lipids. Free ribosomes produce proteins for cells to use.
- also from the vcaa 2018 exam 1b:
My chosen organelles was  rough Endoplasmic reticulum, Golgi apparatus and mitochondria. The report says vesicles is also an option. Are vesicles considered an organelle?

Yeah they are

- Also what are the specifics in terms of cultural evolution of each hominin species do we need to know? For eg do we need to know homo erectus was the first to discover fire.

You don't need to know anything about what specific species did.

- Also while we are on the topic, what do we need to know about Australopithecus genus(I think its a genus idk lmao). How do they relate Homo?

Just trends between australopithicus and homo so things like changes to teeth, pelvis stucture, relative arm/leg length, etc.

- I also kinda keep messing up on what can pass through the plasma membrane, any good tips on how to remember what can pass through? especially when determining whether a molecule is small enough to pass through or not. 
Thnx for the help

Small hydrophillic molecules, and small-medium sized hydrophobic molecules. charged molecules/medium hydrophillic need a channel protein. Large hydrophobic and hydrophilic may either need a channel protein or endocytosis depending on size. The only hydrophillic molecule that you need to remember specifically is water - everything else will be described as a small molecule in the stem of the question.

[Comet striker]

From the ATAR notes exam, 3e:
By what mechanisms may protein synthesis be increased by this pathway(signalling molecule causes changes in gene expression)?
Answer:

Spoiler

Increasing transcription and/or translation. The production of mRNA can be increased by upregulating
the production or activity of relevant transcription factors or upregulating the translation of each
mRNA i.e. increase the amount of times each strand of mRNA is translated.

I wrote along the lines of increasing transcription by activating more RNA polymerase and increasing the rate of translation by producing more tRNA molecules. Would I get any marks for this?