Second in a series of 3 blood type questions questions. A man with blood type A marries a woman with blood type B. Many years later they both die suddenly, leaving a substantial estate but no will. Four people turn up and claim to be the couple's children. One person is A, one B, one AB, and one O. None seem to know each other and each claims the others are frauds. You are hired by one of the kids to look up the medical records of the grandparents. You find the man's parents were AB and B; the woman's parents were both AB. Assuming you were hired by the legitimate heir, who is clearly not your employer? (Who is ruled out by your research?)

Answer: O.

Explanation:

The odd one out is person with O because he/she does not have a comprehensive recessive allele from both of the parents to give a genotype of OO. Therefore, the individual cannot be a member of the family.

Analysis.

The late man's parents were blood groups AB and B. Therefore the possible combination of blood groups for their kids which the man was one of them were; A, AB, B. hence the late man can either be A, AB or B blood group.

Likewise, his wife parents were both AB blood group. Therefore, their kid's blood groups must be one of these blood groups A, AB, and B.

Although the genotype of the grandfather were BB, BO, it lacks a complimentary O allele from the wife (grandmother) to give a genotype OO for blood group O. So this dd not appear in the pedigree.

Note=there was no appearance of O genotype in the family pedigree, so it is not possible for the blood group O to appear in the generation