Question

An M blood type daughter is born to a mother who has type M blood group and a father who has type N. Which of the following is true?

(a) The father of the child is someone else

(b) The mother of the child is someone else

(c) This is a normal case

(d) The child has genotype M/N

This question was posed to me in semester exam.

Query is from Incomplete Dominance and Codominance in division Extension and Deviation from Mendelian Genetic Principles of Cytogenetics

Answer 1

The correct choice is (a) The father of the child is someone else

The best I can explain: MN blood group shows codominance between two alleles M and N. Thus, the daughter to MM mother and NN father should have been MN. But as the daughter is MN, the father of the child is some other man.