Question

What are the genotype and phenotype ratios of the potential offspring when a man who is heterozygous for type A blood marries a woman who has type B blood and whose mother had type O blood?

P__X__

Genotypic ratio ?
Phenotypic ratio?

Answer 1

If a man is heterozygous for type A, his genotype should be IA, i.

Although the woman has type B blood, her mother has type O blood so she must have inherited an i allele to her daughter. Hence, the genotype of the woman is IB, i.

When you draw a cross for IA, i and IB, i , there will be four possible genotypes (IA, i , IB, i , IAIB and ii) (see the photo attached below)

So, the genotypic ratio is 1:1:1:1 and the phenotypic ratio is type A = 1, type B = 1, type AB = 1 and type O = 1