A couple with curly haired husband and straight haired wife have all their children curly haired because

Options

A. Both are heterozygous
B. Husband is homozygous and wife is heterozygous
C. Husband is heterozygous while wife homozygous
D. Both are homozygous.

Answer

To solve the question about why a couple with a curly-haired husband and a straight-haired wife have all curly-haired children, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Traits**:
- Curly hair is represented by the dominant allele (C).
- Straight hair is represented by the recessive allele (c).

2. **Determine the Genotypes of the Parents**:
- The husband has curly hair. Since curly hair is dominant, he can either be homozygous dominant (CC) or heterozygous (Cc).
- The wife has straight hair. Since straight hair is recessive, her genotype must be homozygous recessive (cc).

3. **Analyze the Possible Combinations**:
- If the husband is homozygous dominant (CC) and the wife is homozygous recessive (cc), the possible genotype for their children can be determined by a Punnett square:
- All offspring will inherit one allele from each parent:
- From the husband (C) and from the wife (c).
- This results in all children having the genotype (Cc).

4. **Determine the Phenotype of the Offspring**:
- Since (C) is dominant over (c), all children with the genotype (Cc) will exhibit curly hair.

5. **Conclusion**:
- Therefore, the reason all children have curly hair is that the husband is homozygous dominant (CC) for curly hair, and the wife is homozygous recessive (cc) for straight hair. This results in all children being heterozygous (Cc), displaying the curly hair phenotype.

### Final Answer:
The couple has all curly-haired children because the husband is homozygous dominant (CC) for curly hair, while the wife is homozygous recessive (cc) for straight hair, resulting in all children being heterozygous (Cc) and exhibiting curly hair.

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