What ratio is expected in offsprings if father is colour blind and mother's father was colour blind

Options

A. 50% daughter – colour blind
B. All the sons are colour blind
C. All the daughters colour blind
D. All the sons are normal

Answer

To solve the problem of determining the expected ratio of offspring when the father is color blind and the mother's father was also color blind, we can follow these steps:

### Step 1: Determine the Genotypes
- **Father's Genotype**: Since the father is color blind, his genotype will be XcY (where Xc represents the X chromosome with the color blindness allele).
- **Mother's Genotype**: The mother’s father is color blind, which means he has the genotype XcY. However, we do not have information about the mother's mother, so we will assume she is normal (XX). Therefore, the mother must be a carrier, which means her genotype is XcX (one allele for color blindness and one normal allele).

### Step 2: Set Up the Punnett Square
- The gametes from the father (XcY) and the mother (XcX) will be used to create a Punnett square.
- The father's gametes: Xc and Y
- The mother's gametes: Xc and X

### Step 3: Fill in the Punnett Square
- The Punnett square will look like this:

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

### Step 4: Analyze the Offspring
From the Punnett square, we can see the possible genotypes of the offspring:
1. XcXc (Daughter - Color Blind)
2. XcX (Daughter - Carrier)
3. XcY (Son - Color Blind)
4. XY (Son - Normal)

### Step 5: Determine the Ratios
- **Daughters**:
- 1 daughter is color blind (XcXc)
- 1 daughter is a carrier (XcX)

- **Sons**:
- 1 son is color blind (XcY)
- 1 son is normal (XY)

### Step 6: Calculate the Expected Ratios
- **Daughters**: 50% are color blind (1 out of 2)
- **Sons**: 50% are color blind (1 out of 2)

### Conclusion
The expected ratio of color blind offspring is:
- 50% of daughters are color blind
- 50% of sons are color blind