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Principles of Inheritance and Variation. — Bio Zoology STD 12 — Question

Tamilnadu BoardEnglish MediumSTD 12Bio ZoologyPrinciples of Inheritance and Variation.3 Marks
Question
Explain the genetic basis of Phenylketonuria.
✓

Answer

Phenylketonuria is an inborn error of Phenylalanine metabolism caused due to a pair of autosomal recessive genes. It is caused due to mutation in the gene PAH (phenylalanine hydroxylase gene) located on chromosome 12 for the hepatic enzyme “phenylalanine hydroxylase”.This enzyme is essential for the conversion of phenylalanine to tyrosine. Affected individual lacks this enzyme, so phenylalanine accumulates and gets converted to phenylpyruvic acid and other derivatives. It is characterized by severe mental retardation, light pigmentation of skin and hair. Phenylpyruvic acid is excreted in the urine.
Phenylalanine $\underset{\text { phenylalanine hydroxylase }}{\longrightarrow}$ Tyrosine

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