VCE Biology Exam - 01/11/19 - Discussion/Questions/Solutions

[ssillyssnakes]

I haven’t seen the question but regarding how a vaccine against a allergen could work.
The pollen would be attenuated so it had low reactivity with IgE antibodies (they wouldn’t be able to bind = no mast cell degranulation). However, our immune response would still build up non-IgE antibodies to the pollen antigen. Therefore, when the individual is exposed to the real pollen the pollen specific memory B cells would be able to very quickly produce antibody and sort of neutralise the pollen, preventing any IgE antibodies that are produced from binding as the IgG antibodies have already bound. Much like how you can neutralise a virus by binding antibody and preventing it from interacting with host cells.

I’d doubt they would expect you to describe such detail but I thought I’d share for interest.

That makes sense.... lol I'm screwed then

[darkz]

-Could you say the type of gel in use for 8c would vary the seperation of DNA fragments

Depends how you phrased it e.g. concentration of agarose in the gel can lead to different sizes in the pores -> different separation.

Re: Vaccines & Allergies
I reckon either yes/no will be accepted provided reasonable justification. e.g. No, because it would be impossible to develop a vaccine against all antigens associated with asthma/hayfever and therefore one against thunderstorm asthma as a whole would be impossible.

[PhoenixxFire]

Do you have any idea what would be a good exam score for 45 plus this year with high sac scores

Based off previous years you'd need about 90% for a 44 (with equivalent SACs). It's unlikely to change much this year.

1. For the last question(limitations), can you say that a limitation was that the three students didn't do it in the same time of day?
2. And I still don't understand the thunderstorm asthma vaccine question? Vaccines are used to trigger an immune response, but with this scenario, an immune response is already occurring?
3. For question 1b, can you say that there are over 300 monomers because of how one amino acid is coded for by 3 monomers, therefore 10x3=300 and 6 monomers for START and STOP codons?
4. For 3a, can you say entry via mouth or nose if pathogen has airborne or droplet transmission?
5. For 3d, did you have to specify MHC Class II receptors?
6. For 5c, did you have to specify advantageous phenotypes-natural selection,etc.?
7. For 6aii, can you say chromosomes in WBC?
8. For 8c, can you have said the time that the gel was left on for? Cos if the gel is left on for too long, then all the fragments will settle at the bottom?
9. For 9a, can you say the use of public toilets as a social/economic factor?
10. For 10b, can you say nuclear DNA can be used for DNA hybridisation, wherease mtDNA cannot?

I'm so sorry for so many questions! Don't really think I did too well, after looking at the answers

1. Unlikely that would have any affect on the experiment given temperature was measured.
3. I don't think so. The amino acid sequence being referred to appears to be in the middle of a chain - so no start and stop codons.
4. Yeah. The two ways would have had to be via broken skin and then something to do with getting it into contact with skin covered in chemical barriers not physical (eyes probably would have worked too).
5. We included that because it asks how it's initiated so it seemed important. IDK what the examiners will care about.
6. We weren't really sure. If that question was about a mutation in a location other than BMP4 then it would just be a typical natural selection question. Given it is in BMP4 we thought that they could have been asking why mutations there specifically caused rapid change - which is due to it being a master control gene. We're not really sure what they wanted but I think you could get at least some marks without talking about it.
7. You'd probably get away with that, but it's not really the chromosomes you're testing.
8. Maybe. With the way the question is worded I don't think that's what it's after but you might get a mark for it anyway.
9. No. It asks specifically about transfer from an animal to a human host. It had to be something relating to how they could get infected by an animal.
10. mtDNA can still be used for DNA hybridisation, also the question asks why it was "sequenced" not just why it was extracted so probably not.

I’ve also seen this explanation online about allergen vaccines, and it is what I used in the exam. Do you think it could work, even though it’s not explained as much at the cellular level like you did?

I said that vaccines can be made by exposing allergy sufferers to small amounts of the pollen antigen, in a bid to slowly desentise the body the allergen by basically making them more tolerant the substance so the immune system recognises it as a harmless substance.

That type of desensitisation is called a vaccine in some areas, but I don't think it would be considered a vaccine based on the definition used in VCE.

[Homoerectus]

What was the answer to the limitation question?

I said that the temperatures that they didn’t have enough temperatures to work with and should repeat the experiment with different temperatures

[Sconey]

I said that the temperatures that they didn’t have enough temperatures to work with and should repeat the experiment with different temperatures

I said that they had no control group.

[Kingzone]

I said that they had no control group.

I think either explanations would suffice.


I honesty, I found this exam harder than the previous years.

[oearney]

For SA Q11, the one that was asking about possible reasons leading to the two isolated errors of student 2's measurements, which were random errors, was it okay to write human errors, like incorrect measurements of components and starting the timer later? Are human errors random errors?

[Larz_acccccccccccccccccccccc]

for 4c, wouldn't providing a low dose of an allergen in the form of a vaccine be dangerous as the allergen would bind to the antibodies on the mast cells and cause then to release histamines? Isn't that why people take antihistamines?

For 7b, could the answer possibly be that the reason bissons became extinct is from overhunting from humans

could an option for 11e be that the solutions were not measured with accurate measuring materials improve by measuring with micropipette

[cookielife]

What study score would be equivalent to around 86-87% in SACS and exam?

[interessant]

 In the pdf, the answers for 6dii, was it a frameshift mutation, or just a point substitution?

[PhoenixxFire]

For SA Q11, the one that was asking about possible reasons leading to the two isolated errors of student 2's measurements, which were random errors, was it okay to write human errors, like incorrect measurements of components and starting the timer later? Are human errors random errors?

Yep human errors are fine. Random errors are ones that pop up in random parts of the experiment, rather than consistently across the whole thing.

for 4c, wouldn't providing a low dose of an allergen in the form of a vaccine be dangerous as the allergen would bind to the antibodies on the mast cells and cause then to release histamines? Isn't that why people take antihistamines?

For 7b, could the answer possibly be that the reason bissons became extinct is from overhunting from humans

could an option for 11e be that the solutions were not measured with accurate measuring materials improve by measuring with micropipette

4c. Nope. Allergens can be modified so that they can trigger an immune reaction but not bind to IgE (like how pathogens can be altered to not cause disease).

7b. In reality, no because human populations then wouldn't have been large enough to cause that, but it might be accepted.

11e. That's not really what the question is asking for - a limitation isn't the same as a source of error. It would depend how lenient the markers are being.

What study score would be equivalent to around 86-87% in SACS and exam?

Assuming no scaling to sacs, probably around 40ish.

In the pdf, the answers for 6dii, was it a frameshift mutation, or just a point substitution?

6dii. Asked about a deletion, so it was a frameshift mutation. 6di. was a point substitution.

[jackcameronn]

"the use of chemical agents against pathogens including the distinction between antibiotics and antiviral drugs with reference to their mode of action and biological effectiveness."
can you infer from this that you should have to know specific antibiotics and their mode of action, or just have a rough idea overall. Multiple choice question on penicillin got me fuming

[PhoenixxFire]

"the use of chemical agents against pathogens including the distinction between antibiotics and antiviral drugs with reference to their mode of action and biological effectiveness."
can you infer from this that you should have to know specific antibiotics and their mode of action, or just have a rough idea overall. Multiple choice question on penicillin got me fuming

Yeah I thought that question was unreasonable. It could be expected that you know about the ways in which antibiotics work (covered under "mode of action") but I don't think it's fair to expect you to know how penicillin specifically works - antibiotics can work in multiple ways, including disrupting cell membranes and protein synthesis, which were both other options (although not worded like that). If only one of the answers was something that any antibiotic does then I'd say it's fine, but that wasn't the case with that question meaning that it did require you to know about penicillin specifically.

[Bri MT]

Yep human errors are fine. Random errors are ones that pop up in random parts of the experiment, rather than consistently across the whole thing.

Slight refinement: random errors act in a random direction whereas systematic errors consistently act in the same direction.

This is why you can reduce the impact of random errors (but not systematic errors) by doing multiple trials and averaging

In fact,  random errors are likely to be from humans whereas systematic errors are more likely to be from the apparatus and/or procedure

[3086]

what if you wrote time for the limitation question and said you could use a digital timer which could be more accurate than humans stopping the stop watch?