Colour blindness is characterized by

Options

A. absence of rod cells in retina
B. absence of cone cells in retina
C. absence of lustre of lens
D. lack of colour pigments in the eye

Answer

### Step-by-Step Solution:

1. **Understanding Color Blindness**:
- Color blindness is a condition that affects the ability to distinguish between different colors, primarily red and green. It is often due to genetic factors.

2. **Identifying the Genetic Basis**:
- Color blindness is classified as a Mendelian disorder, specifically an X-linked recessive disorder. This means the gene responsible for color blindness is located on the X chromosome.

3. **Gender Differences in Expression**:
- The condition is more prevalent in males than females. Males have one X chromosome (XY), so if that X chromosome carries the gene for color blindness, they will express the condition. Females have two X chromosomes (XX), so if one X chromosome is affected, the other can compensate, often making them carriers without expressing the condition.

4. **Role of Cone Cells**:
- Color vision is primarily dependent on cone cells in the retina, which contain pigments that absorb different wavelengths of light corresponding to different colors.

5. **Evaluating the Options**:
- **Option 1**: Absence of rod cells in retina - **Incorrect**. Rod cells are responsible for vision in low light and do not play a role in color differentiation.
- **Option 2**: Absence of cone cells in retina - **Incorrect**. Color blindness is not due to the absence of cone cells but rather a defect in the pigments within these cells.
- **Option 3**: Absence of luster of lens - **Incorrect**. The lens of the eye does not affect color perception; it merely focuses light.
- **Option 4**: Lack of color pigments in the eye - **Correct**. Color blindness is characterized by a defect in the pigments in the cone cells, which leads to difficulty in distinguishing colors.

6. **Conclusion**:
- The correct characterization of color blindness is the lack of color pigments in the eye.

### Final Answer:
Color blindness is characterized by a lack of color pigments in the eye.

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