The best example for pleiotropy is :-

Options

A. Skin colour
B. Phenylketoneuria
C. Colour Blindness
D. ABO Blood group

Answer

**Step-by-Step Text Solution:**

1. **Understanding Pleiotropy**:
- Pleiotropy is a genetic phenomenon where a single gene influences multiple phenotypic traits. This means that one gene can affect various characteristics or functions in an organism.

2. **Identifying the Best Example**:
- The question asks for the best example of pleiotropy. We need to find a condition where one gene mutation leads to multiple symptoms or traits.

3. **Analyzing the Options**:
- We consider various conditions and their genetic basis:
- **Phenylketonuria (PKU)**: This is a genetic disorder caused by a mutation in the gene that codes for the enzyme phenylalanine hydroxylase. This enzyme is responsible for converting phenylalanine (an amino acid) into tyrosine. When this enzyme is non-functional, phenylalanine accumulates in the body, leading to various symptoms.
- **Skin Color**: This trait is controlled by multiple genes (polygenic inheritance), not a single gene.
- **Color Blindness**: This condition is linked to specific genes on the X chromosome and is an example of crisscross inheritance, not pleiotropy.
- **ABO Blood Grouping**: This is an example of co-dominance, where two alleles are expressed equally, and does not illustrate pleiotropy.

4. **Conclusion**:
- Since phenylketonuria (PKU) is caused by a single gene mutation that leads to multiple phenotypic expressions (such as mental retardation, skin rashes, and developmental issues), it is the best example of pleiotropy.

5. **Final Answer**:
- The best example for pleiotropy is **Phenylketonuria (PKU)**.

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