MN ABO and Rh are autosomal blood types in man A fourth bloo

MN, ABO, and Rh are autosomal blood types in man. A fourth blood type, Xg is X-linked. Xg plus is dominant. A woman whose blood type is M,A, Rh plus, Xg minus (M/M, A/A, Rh+/Rh+, Xg-/Xg-) marries a man whose blood type is N, B, Rh negative and Xg plus (NN, BB, Rh-/Rh-, Xg+/Y). The blood type of their SON(s) will be:

The answer is MN, B, Rh plus, Xg minus

But I keep getting MN, AB, Rh plus, Xg minus…..What am I doing wrong?

Solution

The gametes of man will be N, B, Rh-, Y and N, B, Rh-, X

The gametes of woman will be M, A, Rh+, Xg-

Blood type of sons will be M/N, A/B, Rh+/Rh-, Xg-/Y

So, all the sons will be MN, AB, Rh plus, Xg minus. Your answer is correct, and the answer given is wrong. Please note, it can never be \"B\" blood group because \'A\' allele will come from the mother side and is autosomal.

The answer can be \'B\' only if autosomal \'A\' allele is silenced in men; or there is a genetic abnormality. Anything, like that is not given in the question.