Question

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:

• A. Both Statement I and Statement II are correct
• B. Both Statement I and Statement II are incorrect
• C. Statement I is correct but Statement II is incorrect
• D. Statement I is incorrect but Statement II is correct

Hint:

Phenylketonuria: \[ \text{Deficiency of phenylalanine hydroxylase} \] It is a classic example of: \[ \text{pleiotropy} \]

Answer 1

The Correct Option is A

Step 1: Analyze Statement I
• Phenylketonuria is a genetic disorder caused by mutation in a single gene.
• This single gene affects multiple traits such as mental development, skin pigmentation and metabolism.
• A single gene influencing multiple phenotypic traits is called: \[ \text{pleiotropy} \] Thus: \[ \text{Statement I is correct} \]
Step 2: Analyze Statement II
• In phenylketonuria, the enzyme: \[ \text{phenylalanine hydroxylase} \] is absent or deficient.
• Normally this enzyme converts: \[ \text{phenylalanine} \rightarrow \text{tyrosine} \]
• Due to enzyme deficiency, phenylalanine accumulates in body tissues. Thus: \[ \text{Statement II is correct} \] Therefore: \[ \boxed{\text{Both Statement I and Statement II are correct}} \] Hence: \[ \boxed{\text{(A)}} \]