Biology Exam Chat + Exam Copy + Answers (now)

[gen.mayu]

Well, I thought that the homozygous recessive would definitely be the answer. I assumed they wanted you to say
let O = normal, let o = disease.

By definition, if they are homozygous dominant, then they are normal - meaning they carry no traces of the disease, therefore even if they were homozygous, it doesn't matter because they are homozygous normal. Therefore, by definition, a homozygous normal hourse isn't going to drop dead at birth just because it had a homozygous genotype. That's what I think at least, -shrugs-

Also great news about the structure question!

[Panicmode]

Well, I thought that the homozygous recessive would definitely be the answer. I assumed they wanted you to say
let O = normal, let o = disease.

By definition, if they are homozygous dominant, then they are normal - meaning they carry no traces of the disease, therefore even if they were homozygous, it doesn't matter because they are homozygous normal. Therefore, by definition, a homozygous normal hourse isn't going to drop dead at birth just because it had a homozygous genotype. That's what I think at least, -shrugs-

Also great news about the structure question!

That's what I got too, and what a lot of other people wrote as well.

Btw, it's not a specific horse species it's a particular breed (same species). Therefore, all horse breeds would have to be heterozygous if this was to occur. The inference that was meant to be made is that because she's heterozygous and unaffected, the trait must be recessive. This was probably an unfair extrapolation to ask of students who have only completed Unit 4 biology, but nonetheless, it was the one to be made.

All this information about OWLS being both dominant and recessive is irrelevant. When considering the trait, lethality it is most definitely recessive. The fact that it shows aspects of incomplete dominance in other traits (ie. overo colouring, frailty) is irrelevant when only considering this one trait.

I agree, the question was ambiguous as fuck and asked a lot of students; but I don't think the other answer is plausible... sorry x_x (Just my opinion)

[LittleMunckin]

yay! i got 1/4 but because of the damn ambiguousness of the question (for the second one), i removed the dead from the probability- but hopefully they might accept it. doubtful though

[Reckoner]

yay! i got 1/4 but because of the damn ambiguousness of the question (for the second one), i removed the dead from the probability- but hopefully they might accept it. doubtful though

I did that too. In the working out space I clearly identified why I removed them from the probability, so 9/16 is written somewhere on there as working, just not on the answer line. Hopefully it gets awarded the mark. 

[HERculina]

Oh man, totally got question 5 wrong 
but seriously, in exam conditions when we're all  rushing they should at least make the question less ambiguous

[LittleMunckin]

VCAA have really screwed us over this year!! All we can hope is that they see the errors in their ways!

[LittleMunckin]

But Bazza do you agree that my logic makes sense?

[Panicmode]

But Bazza do you agree that my logic makes sense?

Hmm, I understand your logic, just don't think it exactly applies to this circumstance. The question was, "what is the chance that Penny has a foal that is phenotypically normal?"

Therefore, it she had a foal with OWLS that died shortly after birth (which is what OWLS does) then that foal would be considered phenotypically atypical and so should be included in the calculation. What did you do, say the probability of a normal foal was 3/4? (not including the foals that died?)

[banditkeith]

See

But Bazza do you agree that my logic makes sense?

Hmm, I understand your logic, just don't think it exactly applies to this circumstance. The question was, "what is the chance that Penny has a foal that is phenotypically normal?"

Therefore, it she had a foal with OWLS that died shortly after birth (which is what OWLS does) then that foal would be considered phenotypically atypical and so should be included in the calculation. What did you do, say the probability of a normal foal was 3/4? (not including the foals that died?)

See.. I think that question can be interpreted in the other way as well.
Your interpretation does seem more fitting but it can't be denied that it can be interpreted the way Little Munckin thought it to be.
Maybe I am just consoling myself because I put the same thing down (3/4 chance- disregarding dead foals)

Such a bad question that shouldn't have been in there! Lucky it was only a mark

[Reckoner]

The question said "died at birth", so when do they actually die? I interpreted it as the foals that had the OWLS were born dead (if you can be born dead?), which I thought would mean they would be removed (making it 3/4). Only way of knowing is waiting though.

[Panicmode]

The question said "died at birth", so when do they actually die? I interpreted it as the foals that had the OWLS were born dead (if you can be born dead?), which I thought would mean they would be removed (making it 3/4). Only way of knowing is waiting though.

I understand, you mean still born. Even then though, I counted them as a foal she had and so included it in my calculations.

[simpak]

The chance that Penny has a foal that dies at birth considers the OLWS locus only.
The chance that Penny has a foal that is phenotypically normal must consider both HERDA and OLWS.
Fail to see how the chance of the foal being normal is 3/4 for that question, taking the above into consideration.

[Panicmode]

The chance that Penny has a foal that dies at birth considers the OLWS locus only.
The chance that Penny has a foal that is phenotypically normal must consider both HERDA and OLWS.
Fail to see how the chance of the foal being normal is 3/4 for that question, taking the above into consideration.

My thoughts exactly. What they're arguing is that any foal with OWLS wouldn't come to term and so if she were to have a foal, it is impossible that it be affected by OWLS (as it would've died earlier).

[simpak]

The chance that Penny has a foal that dies at birth considers the OLWS locus only.
The chance that Penny has a foal that is phenotypically normal must consider both HERDA and OLWS.
Fail to see how the chance of the foal being normal is 3/4 for that question, taking the above into consideration.

My thoughts exactly. What they're arguing is that any foal with OWLS wouldn't come to term and so if she were to have a foal, it is impossible that it be affected by OWLS (as it would've died earlier).

Okay now I understand.  Nup, should still be 9/16.

[polkadot]

oh you are joking.. i wrote 9/16 then crossed it off and wrote 3/4, great -.-