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Help with biology questions

Hello! Would anyone be able to help with a few questions from the 2018 NSAA? I tried screenshotting the questions but couldn't figure out how to insert them into this post (I'm terrible with technology) so I've linked the paper here and added the page numbers where the question is found, if that's okay.

https://www.undergraduate.study.cam.ac.uk/sites/www.undergraduate.study.cam.ac.uk/files/publications/natural_sciences_admissions_assessment_2018.pdf

Q55) pg 50. I put C as I thought the bloodworm, which feeds on fish, would be in abundance when fish populations are high at 1 and 3, and that the stonefly (guessing it eats algae) would be high at 2 when there's lots of algae. I can't figure out why the answer is F (the other way around) 🥴

Q65) pg 59. I put D as I thought if person P had the mutation, they would have to have the condition as it's a dominant genetic condition. Therefore I thought maybe the mutation occurred early in person R's development as they're the only one to have it. The answer is F.

Q71) pg 65. I thought statement 1 made sense since instead of the resistant insects breeding together and creating more resistant offspring with homozygous recessive alleles, if they bred with susceptible insects there would be more susceptible offspring with heterozygous and homozygous dominant alleles. So I put F. The answer is G, but I don't understand why statement 2 is correct; at school we were taught that mutations occur randomly so the reason for there being fewer resistant insects in refugia is because there isn't a selective pressure selecting for pesticide resistance genes and not because there are fewer resistance-giving mutations occurring. Hope that makes sense 😅

Q72.. last q :biggrin: ) pg66. The right answer is F but I don't get why statement 3 is correct. The alleles for the enzyme-coding gene will surely be different, so the base sequence will have to be different. Since the new enzyme is non-functioning, there must be a change in amino acid(s) at the active site which would require a base sequence change.

Sorry for all these questions, and for not being able to attach them to this post directly! Any help with any of these will be greatly appreciated as I think I've driven myself half mad mulling over them XD
(edited 5 months ago)
Original post by vera8
Hello! Would anyone be able to help with a few questions from the 2018 NSAA? I tried screenshotting the questions but couldn't figure out how to insert them into this post (I'm terrible with technology) so I've linked the paper here and added the page numbers where the question is found, if that's okay.

https://www.undergraduate.study.cam.ac.uk/sites/www.undergraduate.study.cam.ac.uk/files/publications/natural_sciences_admissions_assessment_2018.pdf

Q55) pg 50. I put C as I thought the bloodworm, which feeds on fish, would be in abundance when fish populations are high at 1 and 3, and that the stonefly (guessing it eats algae) would be high at 2 when there's lots of algae. I can't figure out why the answer is F (the other way around) 🥴

Q65) pg 59. I put D as I thought if person P had the mutation, they would have to have the condition as it's a dominant genetic condition. Therefore I thought maybe the mutation occurred early in person R's development as they're the only one to have it. The answer is F.

Q71) pg 65. I thought statement 1 made sense since instead of the resistant insects breeding together and creating more resistant offspring with homozygous recessive alleles, if they bred with susceptible insects there would be more susceptible offspring with heterozygous and homozygous dominant alleles. So I put F. The answer is G, but I don't understand why statement 2 is correct; at school we were taught that mutations occur randomly so the reason for there being fewer resistant insects in refugia is because there isn't a selective pressure selecting for pesticide resistance genes and not because there are fewer resistance-giving mutations occurring. Hope that makes sense 😅

Q72.. last q :biggrin: ) pg72. The right answer is F but I don't get why statement 3 is correct. The alleles for the enzyme-coding gene will surely be different, so the base sequence will have to be different. Since the new enzyme is non-functioning, there must be a change in amino acid(s) at the active site which would require a base sequence change.

Sorry for all these questions, and for not being able to attach them to this post directly! Any help with any of these will be greatly appreciated as I think I've driven myself half mad mulling over them XD

Edited:
For question 65, mutation at p in the egg cell from meiosis.
Ignore the unedited version of this post, I got the key mixed up
(edited 5 months ago)
IMG_5267.jpeg
Reply 3
Original post by BankaiGintoki
IMG_5267.jpeg


Thank you so much for your replies, I think I get those now! :smile: Just checking that for Q71 statement 2 is correct since the pesticide is mutagenic and causes a higher rate of mutations overall, increasing the likelihood of a resistance mutation occurring?

I'm also impressed at your technology abilities- how did you manage to attach a screenshot to your reply :-O
Original post by vera8
Thank you so much for your replies, I think I get those now! :smile: Just checking that for Q71 statement 2 is correct since the pesticide is mutagenic and causes a higher rate of mutations overall, increasing the likelihood of a resistance mutation occurring?

I'm also impressed at your technology abilities- how did you manage to attach a screenshot to your reply :-O

IMG_5269.jpeg
Reply 5
Original post by BankaiGintoki
IMG_5269.jpeg


Ah thanks so much!
Reply 6
Original post by vera8
Hello! Would anyone be able to help with a few questions from the 2018 NSAA? I tried screenshotting the questions but couldn't figure out how to insert them into this post (I'm terrible with technology) so I've linked the paper here and added the page numbers where the question is found, if that's okay.

https://www.undergraduate.study.cam.ac.uk/sites/www.undergraduate.study.cam.ac.uk/files/publications/natural_sciences_admissions_assessment_2018.pdf

Q55) pg 50. I put C as I thought the bloodworm, which feeds on fish, would be in abundance when fish populations are high at 1 and 3, and that the stonefly (guessing it eats algae) would be high at 2 when there's lots of algae. I can't figure out why the answer is F (the other way around) 🥴

Q65) pg 59. I put D as I thought if person P had the mutation, they would have to have the condition as it's a dominant genetic condition. Therefore I thought maybe the mutation occurred early in person R's development as they're the only one to have it. The answer is F.

Q71) pg 65. I thought statement 1 made sense since instead of the resistant insects breeding together and creating more resistant offspring with homozygous recessive alleles, if they bred with susceptible insects there would be more susceptible offspring with heterozygous and homozygous dominant alleles. So I put F. The answer is G, but I don't understand why statement 2 is correct; at school we were taught that mutations occur randomly so the reason for there being fewer resistant insects in refugia is because there isn't a selective pressure selecting for pesticide resistance genes and not because there are fewer resistance-giving mutations occurring. Hope that makes sense 😅

Q72.. last q :biggrin: ) pg66. The right answer is F but I don't get why statement 3 is correct. The alleles for the enzyme-coding gene will surely be different, so the base sequence will have to be different. Since the new enzyme is non-functioning, there must be a change in amino acid(s) at the active site which would require a base sequence change.

Sorry for all these questions, and for not being able to attach them to this post directly! Any help with any of these will be greatly appreciated as I think I've driven myself half mad mulling over them XD


For Q55, I think it's more the idea that when a predatory population is high, the prey population will be low, which then causes the predators population to fall, prey population then increases and so the cycle continues. Therefore when bloodworm population is high, fish population is low and vice versa, and the same thing goes for stoneflies and algae, hence it's the opposite, I think?
Reply 7
Original post by BankaiGintoki
For 65, mutation occurred at p during meiosis, to produce sperm cells (which had the condition)


If it is P that the mutation occurs in, that would be the egg cells rather than sperm I think, and it could also potentially be something to do with mutations occurring in utero.
Original post by aarynmb
If it is P that the mutation occurs in, that would be the egg cells rather than sperm I think, and it could also potentially be something to do with mutations occurring in utero.

My bad, I got the key mixed up in my head when I was typing the response.
Reply 9
You can also find model solutions on Physics and Maths Tutor for all NSAA papers I think. Here's 2018 Section 1's solutions:
https://www.physicsandmathstutor.com/admissions/nsaa/solutions-2018/
Reply 10
Original post by aarynmb
For Q55, I think it's more the idea that when a predatory population is high, the prey population will be low, which then causes the predators population to fall, prey population then increases and so the cycle continues. Therefore when bloodworm population is high, fish population is low and vice versa, and the same thing goes for stoneflies and algae, hence it's the opposite, I think?



Ohh I remember learning predator/prey cycles at GCSE that makes sense, thanks! 😁
Reply 11
Original post by aarynmb
You can also find model solutions on Physics and Maths Tutor for all NSAA papers I think. Here's 2018 Section 1's solutions:
https://www.physicsandmathstutor.com/admissions/nsaa/solutions-2018/


Thank you!! :biggrin:

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