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Sex linkage exam question

username1204031

I don't understand part aii of this question:

The mark scheme says that it's because hairless males have fathers with hair. But couldn't that be the case anyway? If parents 1 + 2 were both heterozygous and the gene wasn't sex linked, they could each pass on the recessive allele to produce male hairless offspring.

Reply 1

katya_z

I think you might have misunderstood the question - you're right that two heterozygous parents for non sex linked genes could have the same result, but the question has told you that the gene is sex linked. I think it's really asking how you know the gene is on the X chromosome rather than the Y chromosome, and the hairless father does prove that as male offspring will inherit their only X chromosome from the mother, so it makes no difference whether the father has the allele for hairlessness or not. Hope that helped!

Reply 2

beyknowles2

I hate this type of question. I do AQA Human Biology and I just never know what to say for "Use evidence to explain..", I understand dominant and recessive inheritance and sex-linkage, but I just can't answer this type of question.

Reply 3

katya_z

I know, I think it's really badly written :/ It's a bad tactic to have to take but I think that you just have to not overthink it too much - the question is about sex linkage, so your answer should be directly about sex linkage.

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