Question

Four children belonging to the same parents have the following blood groups A, B, AB and O. Hence, the genotypes of the parents are

• A. Both parents are homozygous for 'A' group
• B. One parent is homozygous for 'A' and another parent is homozygous for 'B'
• C. One parent is heterozygous for 'A' and another parent is heterozygous for 'B'
• D. Both parents are homozygous for 'B' group

Answer 1

The correct option is C One parent is heterozygous for 'A' and another parent is heterozygous for 'B'

• The blood group of the children are A, B, AB and O. Their genotypes will be I${}^A$ I${}^O$, I${}^B$ I${}^O$, I${}^A$ I${}^B$ and I${}^O$ I${}^O$ respectively.
• These four genotypes are possible if their parent have a genotype I${}^A$ I${}^O$ and I${}^B$ I${}^O$. Hence one parent with genotype I${}^A$ I${}^O$ is heterozygous for A and has blood group A.
• The other parent with genotype I${}^B$ I${}^O$ is heterozygous for B and has blood group B.
  

So, the correct answer is ' One parent is heterozygous for 'A' and another parent is heterozygous for 'B'