Father's blood group is A and his son has 'O' group. Which of the blood group can not be present in mother?

Options

A. (a) A
B. (b) B
C. (c) O
D. (d) AB

Explanation

To solve the question regarding the blood group of the mother when the father has blood group A and the son has blood group O, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Blood Group Genetics**:
- The ABO blood group system is controlled by three alleles: IA (A), IB (B), and IO (O).
- The possible genotypes for blood groups are:
- Blood group A: IAIA (homozygous) or IAIO (heterozygous)
- Blood group B: IBIB (homozygous) or IBIO (heterozygous)
- Blood group AB: IAIB (heterozygous)
- Blood group O: IOIO (homozygous)

2. **Identify the Father's Blood Group**:
- The father has blood group A. This means his genotype could be either IAIA or IAIO.
- Since the son has blood group O, the father must be heterozygous (IAIO) to pass on the IO allele.

3. **Determine Possible Genotypes of the Mother**:
- For the son to have blood group O (genotype IOIO), he must inherit the IO allele from both parents.
- Therefore, the mother must also have at least one IO allele.
- The possible blood groups for the mother can be:
- Blood group A (IAIO)
- Blood group B (IBIO)
- Blood group O (IOIO)

4. **Identify the Excluded Blood Group**:
- The mother cannot have blood group AB (IAIB) because this genotype does not contain the IO allele.
- Since the son cannot inherit an O allele from a mother with blood group AB, this is the only blood group that cannot be present in the mother.

### Conclusion:
The blood group that cannot be present in the mother is **AB**.