Select the correct statement with respect to phenylketonuria

Options

A. The affected individual lacks an enzyme that converts the amino acid tyrosine to phenylalanine
B. It is an inborn error of metabolism is also inherited as the autosomal recessive trait
C. Accumulation of tyrosine in brain results in mental retardation
D. Tyrosine is converted into phenylpyruvic acid and other derivatives

Answer

To solve the question regarding phenylketonuria (PKU), we need to analyze each of the provided statements carefully.

### Step-by-Step Solution:

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

2. **Analyzing the Statements**:
- **Statement 1**: "The effective individual lacks an enzyme that converts the amino acid tyrosine to phenylalanine."
- **Analysis**: This statement is incorrect. The enzyme that is deficient in PKU is responsible for converting phenylalanine to tyrosine, not the other way around. Therefore, this statement is false.

- **Statement 2**: "It is an inborn error of metabolism inherited as an autosomal recessive trait."
- **Analysis**: This statement is correct. PKU is indeed classified as an inborn error of metabolism and is inherited in an autosomal recessive manner. Therefore, this statement is true.

- **Statement 3**: "Accumulation of tyrosine in the brain results in mental retardation."
- **Analysis**: This statement is incorrect. It is the accumulation of phenylalanine and its byproducts (like phenylpyruvic acid) that can lead to mental retardation, not tyrosine. Therefore, this statement is false.

- **Statement 4**: "Tyrosine is converted into phenylpyruvic acid and other derivatives."
- **Analysis**: This statement is misleading. In PKU, phenylalanine is converted into phenylpyruvic acid due to the lack of the enzyme. Tyrosine does not convert into phenylpyruvic acid in this context. Therefore, this statement is also false.

3. **Conclusion**:
- The only correct statement regarding phenylketonuria is **Statement 2**: "It is an inborn error of metabolism inherited as an autosomal recessive trait."

### Final Answer:
The correct statement with respect to phenylketonuria is: **It is an inborn error of metabolism inherited as an autosomal recessive trait.**

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