VCE Biology Question Thread

[cosine]

Sorry to keep bringing this up but hopefully it can be settled once and for all, is my understanding correct?

• phagocytes and other leukocytes recognise non self using some type of receptor
• immature T cells recognise non self as per antigens displayed on the mhc2 of antigen presenting cells using complementary T cell receptors- these T cells then proliferate into t helper(?) and t killer cells
• killer T cells recognise non self using mhc1 which are themselves 'self antigens' unique to individuals. Any cells displaying the specific (?) non self mhc1 complementary to cytotoxic T cell receptors are attacked
• b cells recognise non self using their antibodies

- Phagocytes and other leucocytes indeed recognise non-self cells through other receptors that are unfortunately not included in VCE Biol

- Immature T cells do not proliferate into T-helper cells. The T helper cells already exist in our body, and once the T-cell receptor ON the T Helper cell binds to the complementary MHC II marker on an Antigen Presenting Cell (Phagocytes), the Helper T cell is activated and proliferates rapidly.

Helper T cells then HELP other cells of the immune system, this is how I remember them. They 'help' Cytotoxic T cells to be activated, in fact, they both have T cell receptors so when an activated Helper T cell binds to the complementary TCR of a Cytotoxic T cell, it 'helps' it to activate and proliferate.

- For 'b cells recognise non self using their antibodies', you need to be more specific. They don't recognise them just by their antibodies, this is very vague, although correct, but ensure you know that transmembrane (embedded onto the membrane) antibodies actually bind to non-self pathogens, and once again, this is not sufficient enough to activate the B cell to proliferate. So, remember which cell helps other immune cells? Thats right, a Helper T cell that is already activated from the SAME pathogen comes to the site, and binds to the antigen that the B cell presents on it's MHC II markers. Upon the formation of the TCR - MHC II complex,  the B cell proliferates into effective plasma and memory B cells.

Everything else is correct xD

[paper-back]

Does chromosome inversion have any effects on the chromosome involved? Wouldn't there be some interruption in the nucleotide sequence?

[cosine]

Does chromosome inversion have any effects on the chromosome involved? Wouldn't there be some interruption in the nucleotide sequence?

Of course, a portion of the chromosome is being inverted, 'flipped around', hence the original sequence of DNA is being altered.

[Biology24123]

- Phagocytes and other leucocytes indeed recognise non-self cells through other receptors that are unfortunately not included in VCE Biol

- Immature T cells do not proliferate into T-helper cells. The T helper cells already exist in our body, and once the T-cell receptor ON the T Helper cell binds to the complementary MHC II marker on an Antigen Presenting Cell (Phagocytes), the Helper T cell is activated and proliferates rapidly.

Helper T cells then HELP other cells of the immune system, this is how I remember them. They 'help' Cytotoxic T cells to be activated, in fact, they both have T cell receptors so when an activated Helper T cell binds to the complementary TCR of a Cytotoxic T cell, it 'helps' it to activate and proliferate.

- For 'b cells recognise non self using their antibodies', you need to be more specific. They don't recognise them just by their antibodies, this is very vague, although correct, but ensure you know that transmembrane (embedded onto the membrane) antibodies actually bind to non-self pathogens, and once again, this is not sufficient enough to activate the B cell to proliferate. So, remember which cell helps other immune cells? Thats right, a Helper T cell that is already activated from the SAME pathogen comes to the site, and binds to the antigen that the B cell presents on it's MHC II markers. Upon the formation of the TCR - MHC II complex,  the B cell proliferates into effective plasma and memory B cells.

Everything else is correct xD

This is correct

[cosine]

What is the accuracy of the attached image? This came from notes on AN. Is it DNA Helicase or RNA polymerase that unwinds the DNA molecule?

[Biology24123]

What is the accuracy of the attached image? This came from notes on AN. Is it DNA Helicase or RNA polymerase that unwinds the DNA molecule?

Transcription- RNA polymerase
DNA replication- DNA helicase

[paper-back]

After an infection, and the pathogen re-invades, does the proliferation of B-memory cells occur only when the antigen of the pathogen engages with it's antibodies or are receptors located on B-memory cells also involved?

[Biology24123]

After an infection, and the pathogen re-invades, does the proliferation of B-memory cells occur only when the antigen of the pathogen engages with it's antibodies or are receptors located on B-memory cells also involved?

Well the receptors are antibodies

[vox nihili]

What is the accuracy of the attached image? This came from notes on AN. Is it DNA Helicase or RNA polymerase that unwinds the DNA molecule?

It may be that in VCE they say it's RNA polymerase, but this is patently untrue. It's actually a so-called transcription factor called TFIIH (a DNA helicase) that unwinds the DNA strands.

[heids]

This came from notes on AN.

Having submitted some hideously incorrect information last year (but I didn't know it was incorrect then, it was what I'd learnt through the year!), I have limited reliance on AN notes.  Heaps of useful stuff, sure; use it, but with a teaspoon or two of salt.

[cosine]

It may be that in VCE they say it's RNA polymerase, but this is patently untrue. It's actually a so-called transcription factor called TFIIH (a DNA helicase) that unwinds the DNA strands.

(Image removed from quote.)

This is why sometimes i hate VCE Biol... So on an exam do I write RNA Polymerase or DNA helicase o.O?

[heids]

This is why sometimes i hate VCE Biol... So on an exam do I write RNA Polymerase or DNA helicase o.O?

I wouldn't say that RNA polymerase is what is taught as correct, rather that it's a common misconception among students.  Anyways, you wouldn't have to write either; you don't have to go into that level of detail on transcription (it's never mentioned in the assessors' reports I think, not totally sure).

[cosine]

I wouldn't say that RNA polymerase is what is taught as correct, rather that it's a common misconception among students.  Anyways, you wouldn't have to write either; you don't have to go into that level of detail on transcription (it's never mentioned in the assessors' reports I think, not totally sure).

Cheers, and thanks for the birthday wish haha xD

How much are we required to know about structural and regulator genes? Is it sufficient enough to just keep in mind that structural genes code for specific amino acids that serve to produce a functioning protein used by the cell or organism, and regulator genes actually produce specific proteins that regulate the activity and transcription of structural genes? Anything else I am missing?

[heids]

Cheers, and thanks for the birthday wish haha xD

How much are we required to know about structural and regulator genes? Is it sufficient enough to just keep in mind that structural genes code for specific amino acids that serve to produce a functioning protein used by the cell or organism, and regulator genes actually produce specific proteins that regulate the activity and transcription of structural genes? Anything else I am missing?

Welcome

Sounds fine to me, assuming you know basically how transcription factors work (which I'm sure you do).  P.S. here's where you could cut on your answers - avoid stuff like 'code for specific amino acids that serve to produce a functioning protein', just say 'code for a functioning protein'.

[Bruzzix]

My question involving spoilers on a VCAA 2013 question. Proceed at your own risk :p

Spoiler

On the 2013 VCAA exam I had an otherwise perfect answer talking about transcription but I said DNA helicase unravels and unwinds the DNA molecule. Before I marked it I read this thread and decided I would only give myself 1 out of the 2 available marks. Should I only get one mark or two for this question?