Question

Of both normal parents, the chance of a male child becoming colour blind is

• A. Possible only when all the four grandparents had normal vision
• B. Possible only when mother’s father was colour blind
• C. Not possible
• D. Possible only when father’s mother was colour blind

Answer 1

The correct option is B

Possible only when mother’s father was colour blind

The correct option is B.

Explanation for Correct option:

1. Color blindness is a recessive X-linked illness. Males inherit their mother's X chromosomes.
2. Only if the mother is at least a carrier of the condition, and if the mother's father was colorblind, may the male child be colorblind.
3. Otherwise, the mother will be normal but a carrier of the disease.
   

Explanation for Incorrect option:

Option A:

1. Even if all four grandparents had normal vision, it's feasible.
2. Through his mother, the youngster receives DNA from his maternal grandpa in a process known as criss-cross inheritance.
   

Option C:

1. Color blindness is a recessive X-linked illness. Males inherit their mother's X chromosomes.
2. Only if the mother is at least a carrier of the condition, and if the mother's father was colorblind, may the male child be colorblind.
3. Otherwise, the mother will be normal but a carrier of the disease.
   

Option D:

1. When the mother’s father was color blind there are chances to be a male to be color blind.
2. Not possible isn't an option.
3. Through his mother, the youngster receives DNA from his maternal grandfather in a process known as criss-cross inheritance.
   

Final answer:
For both normal parents, the chance of a male child becoming color blind is possible only when the mother’s father was color blind.