CBSE AIPMT 1990
Correct Option (d)
Reason : Phenylketonuria was discovered by the Norwegian physician A Fooling in 1934, an autosomal recessive mutation of gene on chromosome 12. Phenylketonuria results when there is a deficiency of liver enzyme phenylalanine
hydroxylase that converts phenylalanine into tyrosine. Increased phenylalanine in the blood interferes with brain development, muscles and cartilage of the legs may be defective and the patients cannot walk properly.