Question

A woman who has blood type A positive has a daughter who is type O positive and a son who is type B negative. Rh positive is a trait that shows simple dominance over Rh negative and is designated by the alleles R and r, respectively.
Which of the following is a possible genotype for the mother?

a. IAIB

b. IAIA

c. ii

d. IAi

e. IBIB

Answer 1

Answer:

option D

Explanation:

There are four possible blood groups (A, B, AB, O)  and six possible genotypes (AA, AO, BB, BO, AB, OO). Since the mother's bloodgroup is blood type A, then her genotype cannot be IAIB, ii(OO) or IBIB. Thus, we are left with the possible genotypes of IAIA (AA) and IAi (AO).

For her to produce a daughter with blood type O (OO), she has to be an heterozygote with the AO, contributing O so that the father assuming he is of blood type A or B negative (AO or BO) can contribute the second O.

For her to produce a son with type B negative which can only be of genotype BO since the mother is an AO (type A positive), he can only get the type B negative (BO) if his father is blood type B negative. this occurs with the mother contributing the O and the father contributing the B and the rhesus negative factor.