A child has blood group O. If the father has blood group A and the mother has blood group B,...

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A child has blood group O. If the father has blood group A and the mother has blood group B,...

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Question:

A child has blood group O. If the father has blood group A and the mother has blood group B, work out the genotypes of the parents and find out the expected genotype of the other offspring.

Context: ABO Blood Locus in Humans

The ABO locus of humans has three alleles,

I A

,

I B

IA,IB

and i (also called A, B and O), that determine the four blood types A, B, AB and O. The

I

A

IA

 and 

I

B

IB

alleles are both completely dominant to the i allele but are codominant with each other. Genotypes

I A

I A

IAIA

 and 

I A

i

IAi

 have type A blood, genotypes 

I B

I B

IBIB

 and 

I B

i

IBi

 both have type B blood, genotype

I A

I B

IAIB

has type AB blood, and genotype ii has type O blood.

Answer and Explanation:

To have a child with type O blood (genotype ii), both parents have to be heterozygotes. The father must have genotype $I^{A}i$ and the mother has genotype $I^{B}i$. Fertilization of an egg with the i allele by a sperm with the iallele produces the ii child. Other possible genotypes and blood types among the children include: $I^A{I}^B$ with type AB blood, $I^{A}i$ with type A blood, and $I^{B}i$with type B blood.

Reference :

www.study.com