What does the term "pleiotropy" refer to in genetics?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. A single gene influencing multiple traits.
Pleiotropy refers to the genetic phenomenon where one gene controls or affects multiple, often unrelated traits in an organism. This happens because a single gene may produce a product—like a protein or enzyme—that functions in several biological pathways. A classic example is the gene responsible for sickle-cell anaemia, which affects blood shape, resistance to malaria, and oxygen transport.
The other options are incorrect:
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Option 2 describes polygenic inheritance, not pleiotropy.
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Option 3 refers to constitutively expressed genes, not genes with multiple effects.
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Option 4 describes environmentally determined traits, not genetically controlled traits.