Haemophilical man marrie a normal homozygous female. The probability of their child beign haemophiliac is

Options

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

Answer

To solve the problem of determining the probability of a child being hemophiliac when a hemophilic man marries a normal homozygous female, we can follow these steps:

### Step 1: Understand the Genetics of Hemophilia
Hemophilia is an X-linked recessive disorder. This means that the gene responsible for hemophilia is located on the X chromosome. Males have one X and one Y chromosome (XY), while females have two X chromosomes (XX). A male with hemophilia has the genotype X^hY (where X^h represents the X chromosome carrying the hemophilia allele), and a normal homozygous female has the genotype XX (both X chromosomes are normal).

### Step 2: Set Up the Parental Genotypes
- Hemophilic man: X^hY
- Normal homozygous female: XX

### Step 3: Create a Punnett Square
To find the probability of their offspring being hemophiliac, we can create a Punnett square. The possible gametes from each parent are:
- From the hemophilic man: X^h and Y
- From the normal homozygous female: X and X

The Punnett square will look like this:

| | X | X |
|---------|-------|-------|
| **X^h** | X^hX | X^hX |
| **Y** | XY | XY |

### Step 4: Analyze the Offspring Genotypes
From the Punnett square, we can see the possible genotypes of the offspring:
1. X^hX (female, carrier of hemophilia)
2. X^hX (female, carrier of hemophilia)
3. XY (male, normal)
4. XY (male, normal)

### Step 5: Determine the Probability of Hemophilia
None of the offspring can be hemophiliac because:
- Females (X^hX) are carriers but not affected.
- Males (XY) are normal.

Thus, the probability of their child being hemophiliac is **0**.

### Final Answer
The probability of their child being hemophiliac is **0**.

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