Charles who has blood type A is married to Emma who has bloo

Charles who has blood type A⁺ is married to Emma who has blood type B⁺ . Their first child is a girl with blood type O^- (O minus). What is the probability that their next child is a boy with AB⁺ blood type? Assume complete penetrance and no new mutations. Express your answer as a percentage rounded to the nearest tenth, e.g. 33.3%

Solution

Charles and Emma with A+ and B+ blood groups had a girl with O- group, means both the parents are heterozygous for both the alleles. Thus, the genotype of Charles is, AO R+R- and the genotype of Emma is, BO R+R-.

The probability of the AB genotype is, AO*BO -à AB (1/4), AO, (1/4), BO (1/4), OO (1/4)

The probability of R- group is, R+R-* R+R- -à R+_ (3/4), R-R- (1/4)

The probability of having a male is, ½

Thus, the probability of AB+ male is = ¼*3/4*1/2 = 3/32 = 0.0935 or 9.35%