A couple believed that they have brought the wrong baby home from the hospital. The wife is of blood group O, her husband of group B and child of group O. could baby be theirs?

Options

A. chances are 50%
B. chances are 100%
C. chances are 25%
D. chances are 75%

Explanation

To determine whether the baby could be the biological child of the couple, we need to analyze the blood groups of the parents and the child using basic principles of genetics.

### Step-by-Step Solution:

1. **Identify the Blood Groups:**
- The wife has blood group O.
- The husband has blood group B.
- The child has blood group O.

2. **Determine the Genotypes:**
- Blood group O is represented by the genotype **ii** (homozygous recessive).
- Blood group B can be either **IBIB** (homozygous) or **IBi** (heterozygous).

3. **Analyze the Wife's Genotype:**
- Since the wife has blood group O, her genotype must be **ii**.

4. **Analyze the Husband's Genotype:**
- The husband has blood group B, which means his genotype could be either **IBIB** or **IBi**.

5. **Cross the Genotypes:**
- **Case 1: Husband is homozygous (IBIB)**
- Cross: ii (wife) x IBIB (husband)
- Possible offspring: All offspring will have blood group B (IBi).
- Conclusion: If the husband is homozygous, the child cannot be blood group O.

- **Case 2: Husband is heterozygous (IBi)**
- Cross: ii (wife) x IBi (husband)
- Possible offspring:
- 50% will be blood group B (IBi)
- 50% will be blood group O (ii)
- Conclusion: If the husband is heterozygous, there is a 50% chance the child can be blood group O.

6. **Final Conclusion:**
- The child with blood group O could be theirs if the husband is heterozygous (IBi). If he is homozygous (IBIB), the child cannot be theirs.