The phenomenon where a single gene can have multiple phenotypic effects is known as:
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Pleiotropy
Option (4) Pleiotropy — Correct. When a single gene shows multiple phenotypic effects, the gene is called a pleiotropic gene and the phenomenon is pleiotropy. In phenylketonuria, for example, one gene mutation causes mental retardation and a reduction in hair and skin pigmentation.
Note: A similar question was also asked in CUET (UG) 2026 on 21-05-2026 (Slot 1).
NCERT Extract:
Pleiotropy – “We have so far seen the effect of a gene on a single phenotype or trait. There are however instances where a single gene can exhibit multiple phenotypic expression. Such a gene is called a pleiotropic gene. The underlying mechanism of pleiotropy in most cases is the effect of a gene on metabolic pathways which contribute towards different phenotypes. An example of this is the disease phenylketonuria, which occurs in humans. The disease is caused by mutation in the gene that codes for the enzyme phenyl alanine hydroxylase (single gene mutation).”