Question

In an Organism, mutation in a single gene exhibits multiple phenotypic expressions. Identify the underlying genetic mechanism in the above instance.

• A. Pleiotropy
• B. Incomplete dominance
• C. Polygenic inheritance
• D. Multiple allelism

Answer 1

The Correct Option is A

Pleiotropy occurs when a single gene influences multiple phenotypic traits.

Example: The gene responsible for Marfan syndrome affects the heart, eyes, and skeletal system.

• Incomplete dominance (B) results in an intermediate phenotype (e.g., pink flowers from red and white parents).
• Polygenic inheritance (C) involves multiple genes contributing to a single trait (e.g., human height).
• Multiple allelism (D) refers to more than two alleles for a gene (e.g., ABO blood groups).

Since one gene affecting multiple traits, the correct mechanism is pleiotropy (A).

Answer 2

Pleiotropy occurs when a single gene influences multiple phenotypic traits.
This differs from:

• (B) Incomplete dominance: Blending of traits (e.g., pink flowers from red and white parents)
• (C) Polygenic inheritance: Multiple genes control one trait (e.g., human height)
• (D) Multiple allelism: A gene with more than two alleles (e.g., ABO blood groups)

Example: Phenylketonuria (PKU) mutation affects both mental development and skin pigmentation.