In man , gene producing the disease phenyl ketonuria also produces an number of abnormal phenotypic traits, which are collelctively syndrome. This gene results mental retardation, widely spaced incisors, pigmented patches on the skin and excessive sweating such types of genes are called

Options

A. Polgene
B. Pleiotropic gene
C. Lethal gene
D. Supplimentary gene

Answer

To solve the question regarding the type of gene responsible for multiple abnormal phenotypic traits in phenylketonuria, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Condition**:
- Phenylketonuria (PKU) is a genetic disorder caused by the deficiency of the enzyme phenylalanine hydroxylase. This enzyme is crucial for the metabolism of the amino acid phenylalanine.

2. **Identify the Effects of the Gene**:
- The gene responsible for PKU not only leads to the accumulation of phenylalanine but also results in several phenotypic traits such as:
- Mental retardation
- Widely spaced incisors
- Pigmented patches on the skin
- Excessive sweating

3. **Define the Type of Gene**:
- A gene that causes multiple phenotypic effects is known as a **pleiotropic gene**. In this case, the single gene (phenylalanine hydroxylase) is responsible for various traits and symptoms.

4. **Eliminate Other Options**:
- **Polygene**: Incorrect, as polygenes involve multiple genes contributing to a single trait.
- **Lethal Gene**: Incorrect, as lethal genes lead to death in homozygous conditions.
- **Supplementary Gene**: Incorrect, as supplementary genes involve two genes contributing to a trait, where one may mask the other’s effect.

5. **Conclusion**:
- The correct answer is that the gene responsible for the multiple phenotypic effects in phenylketonuria is a **pleiotropic gene**.

### Final Answer:
The gene producing the disease phenylketonuria and its associated traits is called a **pleiotropic gene**.

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