Colour blindness occurs due to :

Options

A. Recesive allele in females
B. Dominant allele in males
C. Dominant allele in males
D. Recessive allele in males

Answer

### Step-by-Step Solution:

1. **Understanding Color Blindness**:
- Color blindness, particularly red-green color blindness, is a condition that affects the perception of colors.

2. **Genetic Basis**:
- The genetic basis of color blindness is primarily linked to the X chromosome. This means that the genes responsible for color perception are located on this chromosome.

3. **Inheritance Pattern**:
- Color blindness is inherited in an X-linked recessive manner. This means that the allele responsible for color blindness is recessive and located on the X chromosome.

4. **Alleles in Males and Females**:
- Males have one X and one Y chromosome (XY), while females have two X chromosomes (XX).
- For males, having just one copy of the recessive allele on their single X chromosome will result in color blindness, as there is no corresponding allele on the Y chromosome to mask its effect.
- For females, color blindness would require two copies of the recessive allele (one on each X chromosome) to express the trait.

5. **Conclusion**:
- Therefore, color blindness occurs due to a recessive allele on the X chromosome, and since males have only one X chromosome, they are more likely to express the trait if they inherit the recessive allele.

### Final Answer:
Color blindness occurs due to a recessive allele in males.

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