If a colour blind person marries a normal women whose father was colour blind, then what percentage of the male progeny will be affected ?

Options

A. `0%`
B. `25%`
C. `50%`
D. `75%`

Answer

To solve the question of what percentage of male progeny will be affected by color blindness when a color blind man marries a normal woman whose father was color blind, we can follow these steps:

### Step 1: Understand the Genetics of Color Blindness
Color blindness is a sex-linked recessive trait, which means it is carried on the X chromosome. The alleles can be represented as:
- X^C: Normal vision (dominant)
- X^c: Color blind (recessive)
- Y: Male chromosome

### Step 2: Determine the Genotypes
1. The color blind man has the genotype X^cY.
2. The normal woman has a father who is color blind, which means she must be a carrier. Therefore, her genotype is X^C X^c.

### Step 3: Set Up the Punnett Square
To find the possible genotypes of their offspring, we can set up a Punnett square:

| | X^C | X^c |
|--------|------|------|
| X^c | X^C X^c (Carrier Female) | X^c X^c (Color Blind Female) |
| Y | X^C Y (Normal Male) | X^c Y (Color Blind Male) |

### Step 4: Analyze the Offspring
From the Punnett square, we can see the possible offspring:
- X^C X^c (Carrier Female)
- X^c X^c (Color Blind Female)
- X^C Y (Normal Male)
- X^c Y (Color Blind Male)

### Step 5: Count the Affected Male Progeny
From the results:
- There are 2 males:
- One is X^C Y (Normal Male)
- One is X^c Y (Color Blind Male)

### Step 6: Calculate the Percentage of Affected Males
Out of the 2 male progeny, 1 is color blind. Therefore, the percentage of affected male progeny is calculated as follows:

\[ \text{Percentage of affected males} = \left( \frac{\text{Number of affected males}}{\text{Total number of males}} \right) \times 100 \]

\[ \text{Percentage of affected males} = \left( \frac{1}{2} \right) \times 100 = 50\% \]

### Conclusion
Thus, the percentage of male progeny that will be affected by color blindness is **50%**.

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