A man whose father was colour blind marries a woman who has a colour blind mother and normal father .What percentage of male childern of this couple will be colour blind ?

Options

A. 0.75
B. 0.25
C. 0
D. 0.5

Answer

To solve the problem of determining the percentage of male children who will be colorblind from the given couple, we can follow these steps:

### Step 1: Understand the Genetics of Colorblindness
Colorblindness is a sex-linked recessive trait carried on the X chromosome. Males have one X and one Y chromosome (XY), while females have two X chromosomes (XX). A male will be colorblind if he inherits the colorblind allele (Xh) on his single X chromosome. A female must inherit two copies of the colorblind allele (XhXh) to be colorblind.

### Step 2: Determine the Genotype of the Man
The man’s father was colorblind, which means he must have the genotype XhY (colorblind). Since the man inherits his X chromosome from his mother, and his father contributes the Y chromosome, the man must have inherited the normal X chromosome from his mother. Thus, the man’s genotype is XhY.

### Step 3: Determine the Genotype of the Woman
The woman has a colorblind mother (XhXh) and a normal father (XY). Since the father is normal, he must have contributed a normal X chromosome to the woman. Therefore, the woman’s genotype is XhX (one colorblind allele from her mother and one normal allele from her father).

### Step 4: Set Up a Punnett Square
To find the possible genotypes of their children, we can set up a Punnett square using the genotypes of the parents:
- Father (man): XhY
- Mother (woman): XhX

The possible gametes from the father are Xh and Y, and from the mother are Xh and X. The Punnett square will look like this:

| | Xh | X |
|---------|---------|---------|
| **Xh** | XhXh | XhX |
| **Y** | XhY | XY |

### Step 5: Analyze the Offspring
From the Punnett square, we can see the possible offspring genotypes:
1. XhXh (female, colorblind)
2. XhX (female, carrier but normal vision)
3. XhY (male, colorblind)
4. XY (male, normal vision)

### Step 6: Determine the Percentage of Male Children that are Colorblind
Out of the four possible offspring:
- There are 2 males: XhY (colorblind) and XY (normal).
- Therefore, 1 out of 2 male children will be colorblind.

To find the percentage:
\[ \text{Percentage of male children that are colorblind} = \left( \frac{1 \text{ (colorblind male)}}{2 \text{ (total males)}} \right) \times 100 = 50\% \]

### Conclusion
The percentage of male children of this couple that will be colorblind is **50%**.

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