VCE Biology Question Thread

[vox nihili]

Sorry for all the questions (I had sent these to another source but they haven't gotten back to me so I thought I might as well send these here!) and thanks for anyone who replies!!
1. The study design mentions knowing the major trends in hominin evolution including structural, functional and cognitive changes, and I've been having a bit of trouble differentiating traits into these categories. For example; is increased brain size a structural or cognitive change? And are actions such as migration and tool making considered functional, (not cognitive)?
2. The study design asks for the source and mode of transport of various signalling molecules, including pheromones. I understand how pheromones diffuse through the air, but found a few different answers for their source. So I wanted to know, where are pheromones produced... or where are they emitted from (is there are general answer I could use)?
3. Also in the context of using plasmids to transport foreign DNA into eukaryotic organisms. Are the recombinant plasmids directly inserted into our germ line and/or somatic cells and are functional? Do they somehow get inserted into our chromosomes to be transcribed like our other genes? When asked to describe how they are used to insert genes into our cells I don't really know how to explain this.
4. Concerning block mutations; I've repeatedly read/written that these mutations do not result in any loss of DNA from the organism, however one of the block mutation type is a deletion. If there is a block deletion that arises in a chromosome, can it be assumed that the deleted selection is present on the other chromosome (as a duplication perhaps)?

Thanks for the help!! I hadn't used AN to ask questions before so clearly I've got a few that have piled up whilst studying...

Sorry to double post...on my phone when I’m on AN these days.

4. Nope. Deletion means that the DNA hasn’t been copied from the parent to the daughter strand; therefore you do lose DNA. Whatever source told you otherwise is wrong imo


Person above, don’t apologise for limited knowledge when you’ve just answered three of the questions!

[ezferns]

Can someone pls explain VCAA 2015 Q7c, the given answer makes no sense to me...
I assumed the difference would be different receptors in each cell type therefore binding to different sequences and hence acting as transcriptional factors to express different proteins.

[vox nihili]

Can someone pls explain VCAA 2015 Q7c, the given answer makes no sense to me...
I assumed the difference would be different receptors in each cell type therefore binding to different sequences and hence acting as transcriptional factors to express different proteins.

Hmm this is a rare example of a really bad question by VCAA. Your answer is perfectly reasonable and you would not be expected to know the details of glucocorticoids. Therefore, given your answer is biologically plausible (if not completely correct), then you really should get marks for your answer. Alas, VCAA didn't see it this way.

Basically what they're saying is that the receptor (the same in each cell) behaves differently because there are other regulator proteins that change how the receptor behaves. How you're expected to know that in VCE beats the shit out of me though tbh...

[LifeisaConstantStruggle]

What you have said is correct but the thing that modifies the expression for these intracellular receptors (what the assessor's report refers to as "factors") are regulatory genes.

Edit: I said "code for", was a typo cuz I was rushing hahaha.

[vox nihili]

What you have said is correct but the thing that modifies the expression for these intracellular receptors (what the assessor's report refers to as "factors") are regulatory genes.

Edit: I said "code for", was a typo cuz I was rushing hahaha.

Not sure if this is directed at me or at ezferns.

Saying there are different receptors is reasonable. This could very well explain the difference. 

The expression of the intracellular receptor actually makes no difference in this case. Changing the expression of the receptor merely changes the amount of the receptor in the cell. The factors they refer to here are other proteins that work in tandem with the receptor to change how it behaves in the cell.

[LifeisaConstantStruggle]

It's supposed to be for ezferns, but wow my original answer is actually the correct answer whoops.

[smamsmo22]

Hi again, just a minor question re. the study design. (U4AOS2)
strategies that deal with the emergence of new diseases in a globally connected world, including the distinction between epidemics and pandemics, the use of scientific knowledge to identify the pathogen, and the types of treatments
I was wondering what other people interpreted/ found for “types of treatments”. Antiviral drugs and antibiotics are obviously mentioned later in the study design but I can’t find anything in my textbook referring to types of treatments. If anyone can briefly let me know what they’ve found or how they interpreted it that’d be helpful!

And I just thought I'd ask what type of ethical and social, or ethical, social and biological issues that people have found associated with gene cloning/ DNA profiling/ genetic screening, and transgenic/genetically modified organisms? Obviously there are a variety of answers but if anyone has a couple of simple but effective examples it would be much appreciated, they don't come up much on practice exams and sometimes it takes me a while to come up with something applicable.

Thanks for the help!!!!

[PhoenixxFire]

Identifying pathogens metioned previously here:

There are actually a few ways to identify a pathogen (bacteria or virus, in this case)
Bacteria:
- agglutination test (with specific antibodies)
- precipitation test (to see if a bacterial colony precipitates in the blood of an infected person)
- Western blot test (used to separate and identify proteins specific to a bacteria)
- ELISA (enzyme-linked immunosorbent assay, which is used to detect and count substances such as antibodies, hormones, enzymes and antigens, which indicates the type of bacteria we might be looking for)
Virus (these things are smaller, so we have to use more precise techniques to kinda sort them out)
- ELISA
- X-ray crystallography (which is used to determine the atomic and molecular structure of crystals, can be used to identify viruses of specific shapes and sizes)
- Electron microscope (these things let you see really small things so you can see viruses with this)

Some ethical issues here although not relevant to all the topics you mentioned

Here are some social and ethical implications of DNA profiling (+ pros, - cons)
+ regular health monitoring of individuals can be implemented, and preventative action can be taken on individuals with genetic disorders/diseases.
+ couples can plan their pregnancy, and make preparations based on the results of DNA profiling/screening for their child
+ a negative result on screening/profiling in relation to genetic diseases can often reduce emotional stress
- a positive result of a genetic disease may induce stress, and can be an emotional burden
- DNA profiling and genetic screening can hinder with one's privacy
- DNA profiling and genetic screening can often be inconclusive, and data can be difficult to interpret

Social and ethical implications of genetic cloning (and also genetic engineering technology which produces GMOs)
+ producing enhanced crops, and organisms, which translates to technological advancement
+ higher quality of life
+ alleviate poverty (higher yielding crops)
+ reduce the detrimental effects of diseases (check out golden rice, transgenic rice with beta carotene which turns into vitamin A, to aid with vitamin A deficiencies within poorer nations)
- genetically modified organisms or cloned genes may affect ecosystems as gene flow might occur between natural and modified organisms (some genes may result in a selective advantage, which affects the allele frequencies of populations)
- companies might claim segments of genes as intellectual property (unethical), and charge high prices for any research/development involving the specific gene.
- GMOs can affect the production of traditional food, and might or might not be adequate substitutes for these traditional food items in providing the required nutrition.
- thorough, rigorous and independent testing of GMOs are required to ensure that the segments of cloned genes do not affect the quantity of production, and gene flow between modified and natural populations that can lead to devastating consequences.

Credit to LifeisaConstantStruggle for all the information.

[smamsmo22]

Identifying pathogens metioned previously here:

Thanks for this! In reference to my first question, I think i have interpreted the "types of treatments" incorrectly. I thought it was asking for different ways that the pathogens are eradicated (drugs etc.) but is it actually referring to the different ways that the pathogens are identified? In that case, I can identify those. Thank you!

[PhoenixxFire]

I think it wants identifying and treatment but I don't think we will need to know much more than general information as there are more specific points elsewhere in the SD (relenza, rational drug design)

[Bri MT]

Thanks for this! In reference to my first question, I think i have interpreted the "types of treatments" incorrectly. I thought it was asking for different ways that the pathogens are eradicated (drugs etc.) but is it actually referring to the different ways that the pathogens are identified? In that case, I can identify those. Thank you!

Make sure you know basic stuff like antibiotics don't help against viruses. I would envision this type of question probably being MC rather than SA

[vox nihili]

Make sure you know basic stuff like antibiotics don't help against viruses. I would envision this type of question probably being MC rather than SA

Question 11 (SA) of the sample exam made direct reference to this point, so definitely can be tested
Feel like there was an angry doctor sick of being asked for antibiotics for colds behind that question somewhere

[TheBigC]

Can someone pls explain VCAA 2015 Q7c, the given answer makes no sense to me...
I assumed the difference would be different receptors in each cell type therefore binding to different sequences and hence acting as transcriptional factors to express different proteins.

Your answer is most definitely valid, however, in their answer, they are mainly referring to differential gene expression and by that I mean some genes are active in some cells and not active in others due to regulatory genes 'producing' repressor proteins that inactivate gene expression at specific sites in specific cells. Ultimately, this means that when GCR-complexes bind to GREs, it only promotes transcription in cells with ACTIVE (non-repressed) genes.... hence their answer is also logical (worded poorly in examiner's report I'd say)....

[rainbowsparkles15]

What is the difference between a selection pressure and a selective agent?

Are retroviruses always made of RNA rather than DNA?

[zenith101]

Hey guys, just regarding the 3rd line of defence in the immune system, am i right in saying:
In the cell-mediated response
-Antigen presenting cells (dendrites and macrophages) travel to the lymph nodes where specific T helper cells are present.
- The T helper cells bind to their specific antigen (MHC II markers), and cause a cascade of reactions. Cytokines are released which activate and cause Cytotoxic T cells to differentiate.
- The Cytotoxic T cells then look for and bind self infected cells (MHC I markers)- binding to the cells and secreting proteins destroying them.

- In the humoral response, native B cells bind to their specific antigen and await activation. When cytokines are released from T helper cells- activating B cells, they differentiate and form B memory and plasma cells. The plasma cells release antibodies- that bind to antigens- causing agglutination and engulfment by phagocytosis.
The B memory cells remain in the lymph nodes, and allow quick production of plasma cells --> antibodies, in subsequent exposures.


If there are any other key details i should know/ or my explanations are incorrect, please mention them
Thanks