Given below are two statements:

Statement I: Phenylketonuria is an example of Pleiotropy

Statement II: Affected individuals lack an enzyme which converts phenylalanine into tyrosine

In the light of the above statements, choose the most appropriate answer from the options given below:

Concept:

• Pleiotropy is the phenomenon of a single gene influencing two or more distinct phenotypic traits.
• An example of a pleiotropy is phenylketonuria which is a genetic disorder caused by the low metabolism of the amino acid phenylalanine in the body cells.

Important Points

Statement I: Phenylketonuria is an example of Pleiotropy - CORRECT

• Phenylketonuria (PKU) is a rare genetic condition that causes an amino acid called phenylalanine to build up in the body.
• It is caused by a mutation of the gene responsible for the production of an enzyme called phenylalanine hydroxylase.
• This disorder may result in several conditions in infants including:
  • intellectual disabilities
  • seizures
  • heart problems
  • developmental delays
• PKU is pleotropic as several phenotypic traits are controlled by a single gene.

Statement II: Affected individuals lack an enzyme which converts phenylalanine into tyrosine - CORRECT

• Affected individuals lack the phenylalanine hydroxylase enzyme, which breaks down the amino acid phenylalanine into tyrosine.
• Without this enzyme, levels of the amino acid phenylalanine increase in the blood and damage the nervous system in infants.

Hence, the correct answer is option 1.