An inborn error of metabolism in which the affected individual lacks an enzyme that converts aminoacid phenylalanine into tyrosine is

Options

A. Phenylketonuria
B. Thalassemia
C. Haemophilia
D. Sickle cell anaemia

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for a specific inborn error of metabolism where an individual lacks the enzyme necessary to convert the amino acid phenylalanine into tyrosine.

2. **Identifying the Condition**: The condition that fits this description is known as Phenylketonuria (PKU). In PKU, the body cannot break down phenylalanine due to a deficiency of the enzyme phenylalanine hydroxylase.

3. **Explaining the Consequences**: When phenylalanine is not converted into tyrosine, it accumulates in the body. This accumulation can lead to the production of harmful substances, such as phenylpyruvic acid, which can have toxic effects, particularly on the brain.

4. **Linking to Genetic Factors**: Phenylketonuria is classified as an autosomal recessive disorder. This means that a person must inherit two copies of the mutated gene (one from each parent) to express the disorder. Carriers of the gene (those with one normal and one mutated gene) do not show symptoms but can pass the gene to their offspring.

5. **Conclusion**: Based on the description of the inborn error of metabolism provided in the question, the correct answer is **Phenylketonuria (PKU)**.

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