If mother has 'O' blood group, child also has 'O' group. What can be the blood group of father?

Options

A. (a) O
B. (b) A
C. (c) B
D. (d) all are possible

Explanation

To determine the possible blood group of the father when the mother has an 'O' blood group and the child also has an 'O' blood group, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Blood Group Genetics**: The ABO blood group system is determined by three alleles: IA (A), IB (B), and i (O). The blood group of an individual is determined by the combination of these alleles.

2. **Identify the Mother's Genotype**: Since the mother has an 'O' blood group, her genotype must be homozygous recessive, which is represented as ii (or IOIO).

3. **Identify the Child's Genotype**: The child also has an 'O' blood group, which means the child's genotype is also ii (or IOIO).

4. **Determine Possible Genotypes of the Father**:
- The father can have the following genotypes:
- **O blood group**: ii (IOIO)
- **A blood group**: IAi (heterozygous, IAIO)
- **B blood group**: IBi (heterozygous, IBIO)

5. **Analyze the Inheritance**:
- If the father has an O blood group (ii), he can pass on an 'i' allele to the child.
- If the father has an A blood group (IAi), he can pass on either an 'IA' or an 'i' allele. For the child to have an O blood group, he must pass on the 'i' allele.
- If the father has a B blood group (IBi), he can pass on either an 'IB' or an 'i' allele. Again, for the child to have an O blood group, he must pass on the 'i' allele.

6. **Conclusion**: Therefore, the possible blood groups of the father can be:
- O (ii)
- A (IAi)
- B (IBi)

7. **Final Answer**: The father can have blood groups O, A, or B. Thus, the most suitable answer is that all are possible.