A colourblind man marries a normal lady whose father was colour blind. If it produces two sons & two daughters, how many of them would suffer

Options

A. Both sons
B. Both daughters
C. One son & one daughter
D. Both sons & both daughters

Answer

To solve the question regarding the inheritance of color blindness in the offspring of a colorblind man and a normal woman whose father was colorblind, we can follow these steps:

### Step 1: Understand the Genetics of Color Blindness
Color blindness is an X-linked recessive trait. This means that the gene responsible for color blindness is located on the X chromosome. Males have one X and one Y chromosome (XY), while females have two X chromosomes (XX). For a male to be colorblind, he needs only one affected X chromosome (XcY). For a female to be colorblind, she must have two affected X chromosomes (XcXc). If she has one affected and one normal X chromosome (XcX), she is a carrier but not affected.

### Step 2: Determine the Genotype of the Parents
- The colorblind man has the genotype XcY (affected).
- The normal woman has a father who is colorblind, which means she must have inherited one affected X chromosome from him. Therefore, her genotype is XcX (carrier) because her mother must have provided a normal X chromosome (X).

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

| | Xc (from mother) | X (from mother) |
|----------|------------------|------------------|
| Xc (from father) | XcXc (colorblind daughter) | XcX (carrier daughter) |
| Y (from father) | XcY (colorblind son) | XY (normal son) |

### Step 4: Analyze the Offspring
From the Punnett square, we can see the possible genotypes of the children:
- 1 daughter with genotype XcXc (colorblind)
- 1 daughter with genotype XcX (carrier)
- 1 son with genotype XcY (colorblind)
- 1 son with genotype XY (normal)

### Step 5: Count the Affected Offspring
From the analysis:
- 1 son is colorblind (XcY)
- 1 daughter is colorblind (XcXc)

Thus, out of the four children, **two children (one son and one daughter) would suffer from color blindness**.

### Final Answer
**Two children (one son and one daughter) would suffer from color blindness.**

---