Mother and father of a person with 'O' blood group have 'A' and 'B' blood group respectively. What would be the genotype of both mother and father ?

Options

A. Mother is homozygous for 'A' blood group and father is heterozgous for 'B'
B. Mother is heterozygous for 'A' blood group and father is homozygous for 'B'
C. Both mother and father are heterozygous for 'A' and 'B' blood group respectively
D. Both mother and father are homozygous for 'A' and 'B' blood group respectively

Explanation

To determine the genotypes of the mother and father of a person with 'O' blood group, we need to analyze the inheritance of blood groups based on the ABO blood group system.

### Step-by-Step Solution:

1. **Understand Blood Group Genetics**:
- The ABO blood group system consists of four main blood types: A, B, AB, and O.
- Blood group A can have genotypes IAIA (homozygous) or IAi (heterozygous).
- Blood group B can have genotypes IBIB (homozygous) or IBi (heterozygous).
- Blood group AB has the genotype IAIB.
- Blood group O has the genotype ii (homozygous recessive).

2. **Identify the Child's Genotype**:
- The child has an 'O' blood group, which means the genotype must be ii (both alleles are O).

3. **Determine Possible Parental Genotypes**:
- For the child to have an O blood group (ii), both parents must contribute an O allele.
- This means that at least one parent must have an O allele in their genotype.

4. **Analyze the Mother's Blood Group**:
- The mother has an 'A' blood group. Therefore, her possible genotypes are IAIA (homozygous A) or IAi (heterozygous A).
- Since the child has an O blood group, the mother must be heterozygous (IAi) to provide the O allele.

5. **Analyze the Father's Blood Group**:
- The father has a 'B' blood group. Therefore, his possible genotypes are IBIB (homozygous B) or IBi (heterozygous B).
- Since the child has an O blood group, the father must be heterozygous (IBi) to provide the O allele.

6. **Conclusion**:
- The mother is heterozygous for A (IAi) and the father is heterozygous for B (IBi).

### Final Answer:
- The genotype of the mother is IAi (heterozygous A) and the genotype of the father is IBi (heterozygous B).