The gene disorder phenylketonuria is an example for

Options

A. multiple allelism
B. polygenic inheritance
C. multiple factor
D. pleiotropy

Answer

**Step-by-Step Solution:**

1. **Understanding Phenylketonuria (PKU):**
- Phenylketonuria is a genetic disorder caused by a deficiency in the enzyme phenylalanine hydroxylase. This enzyme is crucial for the metabolism of the amino acid phenylalanine. When this enzyme is deficient or absent, phenylalanine accumulates in the body, leading to various health issues.

2. **Identifying the Nature of PKU:**
- PKU is classified as an "inborn error of metabolism." This means it is a genetic condition that disrupts normal metabolic processes, specifically the metabolism of amino acids.

3. **Analyzing the Options:**
- The question provides four options: multiple allelism, polygenic inheritance, multiple factor, and pleiotropy.
- **Multiple Allelism:** Refers to a gene having more than two alleles (e.g., ABO blood groups).
- **Polygenic Inheritance:** Involves multiple genes influencing a single trait (e.g., height).
- **Multiple Factor:** Refers to genetic variation due to several loci affecting a trait.
- **Pleiotropy:** Occurs when one gene influences multiple phenotypic traits.

4. **Determining the Correct Option:**
- Since PKU is caused by a mutation in a single gene (the PAH gene), which leads to multiple effects (such as intellectual disability, behavioral issues, and other metabolic problems), it is an example of pleiotropy. One gene (the defective PAH gene) results in multiple phenotypic effects.

5. **Conclusion:**
- Therefore, the correct answer to the question is **pleiotropy** (Option D).

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