Colour blindness results from

Options

A. Cones
B. Rods
C. Rods and cones
D. none of the above.

Answer

**Step-by-Step Solution:**

1. **Understanding Color Blindness**:
- Color blindness is a genetic disorder that affects an individual's ability to perceive colors accurately. It is primarily caused by defects in certain cells in the retina of the eye.

2. **Identifying the Photoreceptor Cells**:
- The retina contains two types of photoreceptor cells: cones and rods.
- Cones are responsible for color vision and function best in bright light conditions.
- Rods are responsible for vision in low light conditions but do not detect color.

3. **Genetic Basis of Color Blindness**:
- Color blindness is typically an X-linked recessive disorder. This means that the gene responsible for color blindness is located on the X chromosome.
- Males, having one X and one Y chromosome, are more frequently affected than females, who have two X chromosomes.

4. **Analyzing the Options**:
- **Option A: Cones** - This is correct because defects in cone cells lead to color blindness.
- **Option B: Rods** - This is incorrect as rods do not play a role in color vision.
- **Option C: Rods and Cones** - This is also incorrect since color blindness specifically involves defects in cones, not rods.
- **Option D: None of the above** - This is incorrect as the correct answer is indeed related to cones.

5. **Conclusion**:
- Based on the analysis, the correct answer to the question "Color blindness results from?" is **A: Cones**.

---