Which of the following statements is true for colour blindness ?

Options

A. It is due to a mutation in certain genes present on `21^(st)` pair of the chromosome.
B. It occurs in female as compared to male.
C. The son of the carrier woman has 50% chances of being colour blind.
D. It is an autosomal linked genetic disorder.

Answer

To determine which statement is true regarding color blindness, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Color Blindness**:
- Color blindness is primarily a genetic condition that affects the ability to perceive colors correctly. It is often linked to mutations in genes located on the sex chromosomes, particularly the X chromosome.

2. **Analyzing the Options**:
- **Option 1**: "It is due to a mutation in certain genes present on the 21st chromosome."
- This statement is **incorrect**. Color blindness is not associated with the 21st chromosome; it is linked to genes on the X chromosome.

- **Option 2**: "It occurs in females as compared to males."
- This statement is also **incorrect**. Color blindness is more prevalent in males than in females because males have only one X chromosome (XY), while females have two (XX). If a male inherits an affected X chromosome, he will express color blindness, whereas females can be carriers without expressing the condition due to the presence of a second normal X chromosome.

- **Option 3**: "Son of the carrier woman has 50% chances of being colorblind."
- This statement is **correct**. If a woman is a carrier (XcX), there is a 50% chance that her son (XY) will inherit the affected X chromosome (Xc) and thus be colorblind. The possible combinations for their sons would be XcY (colorblind) and XY (not colorblind).

- **Option 4**: "It is an autosomal linked genetic disorder."
- This statement is **incorrect**. Color blindness is a sex-linked disorder, not an autosomal disorder. It is specifically linked to the X chromosome.

3. **Conclusion**:
- The only true statement regarding color blindness is **Option 3**: "Son of the carrier woman has 50% chances of being colorblind."