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NEETZoologyPrinciples of Inheritance and Variation

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Phenylketonuria is a classic example of pleiotropy in humans. Reason (R): The affected individual lacks an enzyme that converts phenylalanine to tyrosine, which cascades into multiple phenotypic effects like mental retardation and reduction in hair and skin pigmentation. In the light of the above s

Options

  1. ABoth Assertion (A) and Reason (R) are true but Reason (R) is not the correct explanation of Assertion (A).
  2. BAssertion (A) is true but Reason (R) is false.
  3. CBoth Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
  4. DAssertion (A) is false but Reason (R) is true.

Correct answer

C. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).

Step-by-step solution

Assertion (A) is true because pleiotropy occurs when a single gene exhibits multiple phenotypic expressions, and Phenylketonuria is a classic example of this phenomenon in humans. Reason (R) is also true and correctly explains the assertion. Phenylketonuria is caused by a mutation in the gene that codes for the enzyme phenylalanine hydroxylase. This single mutation prevents the conversion of the amino acid phenylalanine to tyrosine, leading to a cascade of multiple phenotypic effects such as mental retardation, and

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