According to the ABO system , the commonest blood group in the human population is (X) while the rarest blood group is (Y) . If the wife has (X) blood group and the husband has (Y) blood group , their children will have which of the following blood groups ?

Options

A. AB and O groups only
B. AB only
C. A and B groups only
D. All four groups

Answer

To solve the problem, we need to analyze the blood groups of the parents and determine the possible blood groups of their children based on the ABO blood group system.

### Step-by-Step Solution:

1. **Identify the Commonest and Rarest Blood Groups:**
- The commonest blood group (X) is O.
- The rarest blood group (Y) is AB.

2. **Determine the Genotypes of the Parents:**
- The wife has blood group O. The genotype for blood group O is **ii** (homozygous recessive).
- The husband has blood group AB. The genotype for blood group AB is **IAIB** (heterozygous).

3. **Gamete Formation:**
- The wife (O blood group) can only produce gametes with the **i** allele.
- The husband (AB blood group) can produce two types of gametes: **IA** and **IB**.

4. **Possible Combinations of Alleles:**
- When we combine the gametes from both parents, we have the following possibilities:
- From the wife (i) and husband (IA): **IAi** (which corresponds to blood group A)
- From the wife (i) and husband (IB): **IBi** (which corresponds to blood group B)

5. **Determine the Blood Groups of the Children:**
- The possible blood groups of the children based on the combinations are:
- Blood group A (from IAi)
- Blood group B (from IBi)

6. **Conclusion:**
- The children can only have blood groups A and B. Therefore, the answer is **C: A and B groups only**.