A woman with straight hair mates with man with curly hair who is known to be heterozygous for that trait. What is he chance that their first child will have curly hair?

Options

A. No chance
B. One in two
C. It is certain
D. One in four

Answer

To solve the question of the chance that the first child of a woman with straight hair and a heterozygous man with curly hair will have curly hair, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Traits and Alleles**:
- Curly hair (C) is dominant.
- Straight hair (c) is recessive.
- The woman has straight hair, so her genotype is **cc**.
- The man has curly hair and is heterozygous, so his genotype is **Cc**.

2. **Determine the Possible Gametes**:
- The woman can only produce one type of gamete: **c** (since she is homozygous recessive).
- The man can produce two types of gametes: **C** (dominant) and **c** (recessive).

3. **Set Up a Punnett Square**:
- Create a Punnett square to visualize the possible combinations of alleles from the parents.

```
C c
----------------
c | Cc | cc |
----------------
```

4. **Analyze the Offspring Genotypes**:
- From the Punnett square, we see two possible genotypes for the offspring:
- **Cc** (curly hair)
- **cc** (straight hair)

5. **Calculate the Probability**:
- Out of the two possible genotypes, one genotype (Cc) results in curly hair and one genotype (cc) results in straight hair.
- Therefore, the probability of having a child with curly hair (Cc) is **1 out of 2**, or **50%**.

### Final Answer:
The chance that their first child will have curly hair is **50%** or **1 in 2**.

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