Question

Genotype	Phenotype
IAIA or IAi	type A blood
IBIB or IBi	type B blood
IAIB	type AB blood
ii	type O blood

A) A case came before People's Court. Mr. and Mrs. Smith (names have been changed to protect the innocent!) had a baby girl named Samantha. Their next-door neighbor, Mr. Jones, filed a suit to gain custody of Samantha, claiming the baby was his. Blood tests were conducted with the following results:

Samantha: type O

Mr. Smith: type AB

Mrs. Smith: type B

Mr. Jones: type A

You are the judge. How would you rule? Explain your answer completely.

B) How would you rule if the blood types had come out as follows? Explain your answer completely.

Samantha: type AB
Mr. Smith: type AB

Mrs. Smith: type B

Mr. Jones: type A

Answer 1

Answer A

Let us assume two situations

Situation 1. Mr and Mrs Smith are the parents of Samantha. The genotypes of the two will be I^AI^B and I^BI^B (or I^Bi), respectively.

Let us use I^Bi notation for Mrs. Smith since Samantha has ii genotye which is actually asked to varify in the question. The offsprings will be like the following Punnet square.

Punnet square1

IAIB	IAi
IBIB	IBi

Situation 2. Instead Mr Jones and Mrs Smith are the parents of Samantha. The genotypes of the two will be I^Aiand I^Bi, respectively. The offsprings will be like the following Punnet square.

Punnet square 2

IAIB	IAi
IBi	ii

It is now clear from the Punnet square 2 that Samantha could be the child of Mr. Jones and Mrs. Smith.

Thus, the case would be in favor of Mr. Jones and his claim for Samantha's custody is right.