A woman with blood group A, whose father had blood group O, marries a man with blood group AB. What is the probability that their first child will be a male with blood group B?

Step-by-step solution

The woman has blood group A, but her father had blood group O (genotype ii ). She must have inherited an i allele from her father, making her genotype heterozygous ( I^ A i ). The man has blood group AB, so his genotype is I^ A I^ B . A cross between the woman ( I^ A i ) and the man ( I^ A I^ B ) produces the following possible genotypes in the offspring: I^ A I^ A (blood group A), I^ A i (blood group A), I^ A I^ B (blood group AB), and I^ B i (blood group B). Out of the four possible combinations, only one results