VCE Biology Questions Thread

prettypink1881

does anyone know if we need to know about reverse transcriptase and why is can't be used for some viirus testing in pcr?

if we do can someone let me know the answer because i've tried searching on google but I can't find anything that relates to any other dot points.

Taaaa76

prettypink1881
I remember hearing about something like this.
Is this from a question in the 2022 exam?

prettypink1881

Taaaa76 yeah question 2c short answer.

prettypink1881

Taaaa76

"Two reasons why RT-PCR cannot be used on all viruses included:
• a suitable probe may not be available or a complementary probe has not been produced
• not all viruses are made of RNA, or the nucleotide sequence in a virus may not be unique enough.
Students who were able to apply their knowledge of complementary sequences to this unfamiliar situation provided suitable reasons."

I get the second option, but I don't understand the first; do you know what suitable probe means?

jessh24

prettypink1881 The stem of that part of the question says the probes attach only to complementary sequences on particular viruses. So if a probe didn't exist with that particular complementary sequence then it wouldn't work because the probes are required for RT-PCR. I think?

jessh24

is divergent and convergent evolution still on the study design?

Taaaa76

jessh24 i think divergent is, not convergent.

All you would really need to know about convergent anyway is that analagous structures is a sign of it. Wouldnt hurt to know about it

stevendort

jessh24 No. In the biology FAQ document, it specifically states that knowledge of convergent and divergent evolution is not needed. You just need to know what homologous, analogous, and vestigial structures are (this is basically convergent and divergent evolution anyways). However, divergent evolution is basically just regular evolution, thus you may need to know it.

Taaaa76

jessh24 that’s what i gathered as well

prettypink1881

jessh24 yeah that makes sense, thanks!!

Meep<3

Does anyone know if we need to know specific ways that scientists use CRISPR technology to modify organisms like non-homologus or homologous end joining?

stevendort

Meep<3 You do not need to know the specifics of NHEJ and HDR. You simply need to know that genes can be knocked in and out.

Meep<3

ohh okk thankss

prettypink1881

does anyone know how the adaptive immune response rejects a transplant organ? is it the same in that apcs engulf the foreign antigens etc, or is it different?

Taaaa76

prettypink1881
Your body rejects an organ when its antigens arent the same as yours, so it will recognise it as non-self and basically initiates the adaptive immune response to get rid of it

Taaaa76

Taaaa76 the same adaptive immune response that involves macrophages engulfing foreign antigens/cells and then oresenting to helper T cells etc etc

prettypink1881

Taaaa76 thanks!

Meep<3

I had a question, when the helper T cells are activated by an antigen-presenting cell, how does it know whether it should activate a B lymphocyte or a cytotoxic T cell? So in other words how does the T helper cell know if it should activate the cell-mediated response or the humoral response?

prettypink1881

Meep<3 I don't think we need to know "how they know", but the cell mediated response will be initiated if the pathogen is intracellular, and has invaded a cell ie a virus. the humoral response will be initiated if the pathogen is an extracellular pathogen. both a t helper cell and a naive t or b cell need to be selected by the same antigen for the response to happen. i think.

Taaaa76

prettypink1881
I thought both were activated regardless wether it was intracellular or extracellular?
So if someone had a bacterial infection, the cell mediated response wouldnt be initated at all?

Meep<3

Ok thank you

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