Lesch Nyhan disease is an X-linked recessive disorder that causes neurological damage in human beings. A survey of 500 males from a caucasion population revealed that 20 were effected with this disorder. What is the frequency of the normal allele in this population ?

Options

A. `9.6`
B. `0.8`
C. `0.096`
D. `96`

Answer

To solve the problem of finding the frequency of the normal allele in the population affected by Lesch Nyhan disease, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the total number of males surveyed**:
- The problem states that a survey of 500 males was conducted.

2. **Determine the number of affected individuals**:
- It is given that 20 males were affected by Lesch Nyhan disease.

3. **Calculate the frequency of affected individuals**:
- The frequency of affected individuals (who have the disorder) can be calculated as:
\[ \text{Frequency of affected} = \frac{\text{Number of affected}}{\text{Total number of males}} = \frac{20}{500} = 0.04 \]

4. **Relate this to the allele frequencies**:
- Since Lesch Nyhan disease is an X-linked recessive disorder, the frequency of the affected males corresponds to the frequency of the recessive allele (denoted as \( q^2 \)). Therefore, we have:
\[ q^2 = 0.04 \]

5. **Calculate the frequency of the recessive allele \( q \)**:
- To find \( q \), we take the square root of \( q^2 \):
\[ q = \sqrt{0.04} = 0.2 \]

6. **Calculate the frequency of the normal allele \( p \)**:
- The frequency of the normal allele \( p \) can be calculated using the relationship \( p + q = 1 \):
\[ p = 1 - q = 1 - 0.2 = 0.8 \]

7. **Conclusion**:
- The frequency of the normal allele in this population is \( 0.8 \).

### Final Answer:
The frequency of the normal allele in this population is **0.8**.

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