Person whose father is colourblind marries a lady whose mother is daughter of a colourblind man. Their children will be

Options

A. All sons colour blind
B. Some sons normal and some colour blind
C. All colorblind
D. All normal

Answer

To solve the question regarding the inheritance of colorblindness in the children of a colorblind man and a woman whose mother is the daughter of a colorblind man, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Genotype of the Colorblind Man**:
- The father of the man is colorblind. Since colorblindness is an X-linked recessive trait, his genotype is XcY, where Xc represents the X chromosome with the colorblind allele.

2. **Determine the Genotype of the Man**:
- The man himself must have inherited a normal X chromosome from his mother (who is not colorblind). Therefore, his genotype is XY (normal vision).

3. **Identify the Genotype of the Woman**:
- The woman’s mother is the daughter of a colorblind man. This means the woman’s mother could either be colorblind (XcXc) or a carrier (XcX). Since the father is colorblind, he must have passed on the Xc chromosome to his daughter. Thus, the woman’s mother must be at least a carrier (XcX).

4. **Determine the Possible Genotypes of the Woman**:
- The woman can either be a carrier (XcX) or have normal vision (XX). Therefore, the possible genotypes for the woman are XcX (carrier) or XX (normal).

5. **Cross the Genotypes of the Man and Woman**:
- If the woman is a carrier (XcX):
- Possible offspring:
- Daughters: 50% XcX (carriers), 50% XX (normal)
- Sons: 50% XcY (colorblind), 50% XY (normal)
- If the woman is normal (XX):
- Possible offspring:
- Daughters: 100% XX (normal)
- Sons: 100% XY (normal)

6. **Conclusion**:
- Since we are considering the case where the woman is a carrier, the children will have a mix of colorblind and normal vision. Therefore, the correct answer is that some sons will be colorblind and some will be normal.

### Final Answer:
The children will be a mix of colorblind and normal, specifically: some sons will be colorblind and some will be normal.

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