IMAT 2O21 Question 26

Hi! Can someone pls help me out on this one?


What this question basically asking is which pedigree chart out of the given answer options is possible only if the trait is expressed as an Autosomal dominant condition.
Autosomal dominant means it is not sex linked and we need just one allele for the phenotype to be expressed.
In option 2 we see an effected father passes the trait to one daughter but not to another (meaning in this case it cannot be sex linked).
This is therefore the answer.

Also, in answer option 2 we can see that both the parents of the F2 generation are affected but one of the offsprings is unaffected so, it’s completely clear that the condition in answer option 2 can’t be due to the recessive alleles as they would have never been able to produce a healthy offspring.
Hope it helps:)

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