Father of a child is colourblind and mother is carrier for colourblindness, the probability of the child being colour blind is

Options

A. `25 %`
B. `50 %`
C. `100 %`
D. `75 %`

Explanation

To solve the problem of determining the probability of a child being colorblind when the father is colorblind and the mother is a carrier for colorblindness, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Genetic Basis of Colorblindness**:
- Colorblindness is an X-linked recessive disorder. This means that the gene responsible for colorblindness is located on the X chromosome, and two copies of the recessive allele are needed for females to express the trait, while only one copy is needed for males.

2. **Determine the Genotypes of the Parents**:
- The father, who is colorblind, has the genotype **XcY** (where Xc represents the X chromosome with the colorblind allele).
- The mother, who is a carrier, has the genotype **XXc** (where X represents the normal vision allele and Xc represents the colorblind allele).

3. **Gamete Formation**:
- The father can produce two types of gametes: **Xc** and **Y**.
- The mother can produce two types of gametes: **X** and **Xc**.

4. **Set Up a Punnett Square**:
- Create a Punnett square to determine the possible genotypes of the offspring.
- The rows will represent the father's gametes (Xc and Y), and the columns will represent the mother's gametes (X and Xc).

| | X | Xc |
|---------|-----------|-----------|
| **Xc** | XcX | XcXc |
| **Y** | XY | YXc |

5. **Analyze the Offspring Genotypes**:
- From the Punnett square, the possible genotypes of the children are:
- **XcX**: Female carrier (normal vision)
- **XcXc**: Female colorblind
- **XY**: Male normal vision
- **YXc**: Male colorblind

6. **Count the Phenotypes**:
- Out of the four possible offspring:
- 1 female carrier (XcX)
- 1 female colorblind (XcXc)
- 1 male normal vision (XY)
- 1 male colorblind (YXc)

- Therefore, 2 out of 4 children are colorblind (1 female colorblind and 1 male colorblind).

7. **Calculate the Probability**:
- The probability of a child being colorblind is the number of colorblind children divided by the total number of children:
- Probability = Number of colorblind children / Total number of children = 2/4 = 1/2 = 50%.

### Conclusion:
The probability of the child being colorblind is **50%**.