Read the given passage and answer the following questions.
Mendelian disorders are mainly determined by alteration or mutation in the single gene. These disorders are transmitted to the offspring on the same lines as we have studied in the principle of inheritance. The pattern of inheritance of such Mendelian disorders can be traced in a family by the pedigree analysis. Most common and prevalent Mendelian disorders are Haemophilia, Cystic fibrosis, Sickle cell anaemia, Colour blindness, Phenylketonuria, Thalassemia, etc. It is important to mention here that such Mendelian disorders may be dominant or recessive.
Phenylalanine in phenylketonuria (PKU) is converted into which compound that accumulates in the brain?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Phenylpyruvic acid
Phenylketonuria (PKU) is an inborn error of metabolism. The affected person lacks the enzyme that changes the amino acid phenylalanine into tyrosine. So phenylalanine piles up in the body and is changed into phenylpyruvic acid and other derivatives. When these build up in the brain they cause mental retardation. Because the kidney absorbs them poorly, they also pass out in the urine.
NCERT Extract:
Mendelian Disorders – “… Phenylketonuria : This inborn error of metabolism is also inherited as the autosomal recessive trait. The affected individual lacks an enzyme that converts the amino acid phenylalanine into tyrosine. As a result of this phenylalanine is accumulated and converted into phenylpyruvic acid and other derivatives. Accumulation of these in brain results in mental retardation. These are also excreted through urine because of its poor absorption by kidney.”