This question refers to the abo blood type locus. remember that the a and b alleles are codominant to each other and both are dominant to the o allele. assume no epistatic interactions with the h locus. a woman is blood type ab. her child is blood type b. she wants to get child support from a man who is blood type a. can this man be the father of the woman's child based on these data?
yes
no

No

Explanation:

If the mother has a phenotype AB, she only can have the genotype . This because A and B are codominant alleles.  The child is blood type A, so he can be heterozygote or homozygote for allele B.  The possible father is blood type A and he can be heterozygote or homozygote for allele A.  Hence, possibles genotypes are:

Mother:

Child:   or

Possible father: or

If the father is  , children of these parents can have the genotypes shown in the first Punnet Square.

And, if the father is  , possible progeny will be the one on the second Punnet Square.

So, it is impossible for this couple to have a son blood type A.

it would lead to upper respiratory infections and pneumonia.

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