Phenylketonuria is an inborn error of metabolism that is inherited as

Options

A. Autosomal recessive trait
B. Sex-linked dominant trait
C. X-linked recessive trait
D. autosomal dominant trait

Answer

### Step-by-Step Text Solution

1. **Understanding Phenylketonuria (PKU)**:
- Phenylketonuria is an inborn error of metabolism, meaning it is a genetic disorder present from birth. It is characterized by the accumulation of phenylalanine, an amino acid, in the body.

2. **Role of Enzyme**:
- The body has an enzyme called phenylalanine hydroxylase, which is responsible for converting phenylalanine into another amino acid, tyrosine.

3. **Cause of PKU**:
- When there is a deficiency or absence of phenylalanine hydroxylase, phenylalanine accumulates in the body, leading to the symptoms associated with PKU.

4. **Genetic Basis**:
- The gene that codes for the enzyme phenylalanine hydroxylase is an autosomal gene. This means it is located on one of the autosomes (non-sex chromosomes).

5. **Inheritance Pattern**:
- PKU is inherited in a recessive manner. This means that an individual must inherit two copies of the mutated gene (one from each parent) to express the disorder. If only one copy is mutated (and the other is normal), the individual will not show symptoms of PKU.

6. **Conclusion**:
- Therefore, the correct answer to the question of how Phenylketonuria is inherited is that it is inherited as an **autosomal recessive trait**.

### Final Answer:
Phenylketonuria is inherited as an **autosomal recessive trait**.

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