Question

In a paternity case, a woman (blood type O) claims a man (type A) whose mother is O to be the father of her

child. Is there any possibility the woman is correct? If so, show the genotypes of the people involved and a likely cross to produce a child with blood type O.

Answer 1

Yes, the mother's claim might be correct.

Please find the genotype of the parents and the cross below

Step-by-step explanation:

Blood group in humans is controlled by three alleles namely; iA, iB, and i. Alleles iA and iB are dominant over allele i but co-dominant when together i.e. iAiB

Based on this, below are the blood types of an individual with the possible genotype;

Blood type A - iAiA or iAi

Blood type B - iBiB or iBi

Blood type AB - iAiB

Blood type O - ii

According to this question involving a paternity case, a woman with blood type O claims a man with blood type A whose mother is type O to be the father of her child. The woman has a genotype 'ii' while the man has a heterozygous genotype 'iAi' because his mother will contribute the 'i' allele.

Hence, using the genotype of the woman (ii) and man (iAi) in a cross as follows; ii × iAi (see attached image for punnet square), the following proportion of offsprings will likely be produced:

(2) iAi - blood type A

(2) ii - blood type O

Therefore, the woman's claim that the man is the father of her child with blood type O (ii) is most likely correct.