VCE Biology Questions Thread

md2112

1. Cytotoxic T cells are involved in an adaptive immune response (cell mediated) and they release chemicals like perforins to induce apoptosis in virally infected cells upon binding to the non self antigen presented on MHC 1 markers of the infected host cell
2. Whereas natural killer cells are involved in the innate immune response. It detects the lack of MHC 1 markers on a host cell and recognises it as “non self” releasing granzymes initiating a death ligand that causes apoptosis

Also can someone please explain the Q9 C ii) of the 2022 sample exam on mtDNA phylogeny - I kind of get it but not fully- espcially the part about “continuous presence” of aboriginal Australian populations

Smartiestarz ok thanks, also do u know how do cytotoxic t cells get activated by t helper cell

md2112 cytotoxic t cells are part of the adaptive cell-mediated response, whereas natural-killer cells are non-specific immune cells part of the innate immune system (second line of defence). Cytotoxic t cells will therefore specifically bind to MHC I markers/antigens it's initial T cell was selected for, whereas natural killer cells will target any foreign MHC I markers it notices on viral infected cells or tumour cells. Also, natural killer cells have killer activation and killer inhibition receptors that indicate whether it kills the cell, whereas cytotoxic t cells are already programmed to kill the cell that they bind to using their t cell receptor.

md2112 Cytotoxic T cells produced from the expansion and differentiation of the selected T cell are activated by Helper T cells via the release of cytokines, as well as through binding to the first MHC I marker it finds on an infected cell. Both allow it to be activated.

guys im confused with the question 1c on the sample exam, it says will the "enzymes for tryptophan sysntehis be produced", can someone please help

_sophiestudies_ thank you so much

outline the humoral response

_sophiestudies_ oh that makes sense, so i could simply talk about attenutation, and it produces a trasncirption termination signal which prevents the expresssion of structural genes and so the enzymes aren't produced

Smartiestarz ^^

what is the difference between social implication and biological implication? and also do we need to include that in sympatric speciation gene flow doesnt occur

Also do we need to know about BMP4 gene

can some1 explain the steps to sympatric speciation regarding howea palms plz

is question 1 short answer from 2021 vcaa exam still relevant?

chemistry1111 no it's not

chemistry1111 Social implication relates to the community (e.g. birth rates, death rates, standard of living) and money/profits. Biological implication relates to the functioning of the organism e.g. better nutrition, reduced risk of disease.
No you do not need to know about the BMP4 gene.

studyingvce2022 Hi there! For a question on sympatric speciation in howea palms I’d say :—

1. There is pre-existing genetic variation in the howea palm population with some palms being able o grow better in acidic soil whereas potters growing better in basic soil (likely due to a prior polyploidy mutation which may have been the source of a new allele)
2. These palms are NOT geographically o isolated, but occupy different niches hence may be exposed to different environments and different selection pressures
3. Which selected for different phenotypes (ex-the difference sin flowering times). Over many generations as the different mutations accummalate, there is so much genetic and phentoypic variation between the palms that
4. They are unable to interbreed to produce viable fertile offspring, hence are considered to be reproductively isolated and have formed different/seperate species