The hereditary defect phenylketonuria is caused by deficiency of
A
Phenylalanine hydroxylase
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B
Fructokinase
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C
Glucokinase
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D
Haemoglobin reductase
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Solution
The correct option is B Phenylalanine hydroxylase Phenylketonuria is an autosomal recessive disorder which is caused due to the deficiency of enzyme phenylalanine hydroxylase. The defect occurs due to the gene present on chromosome 12 gets mutated. This gene is responsible for the formation of phenylalanine hydroxylase which is required in the body for the conversion of amino acid phenylalanine to tyrosine. Tyrosine is needed by the body to create neurotransmitters such as epinephrine, norepinephrine, and dopamine. The accumulation of phenylalanine in the infants causes tremors, stunted growth, eczema and seizures. A dangerous buildup of phenylalanine occurs if one eats protein-rich foods.