Random unidirectional change in allele frequencies that occurs by chance in all populations and especially in small populations is known as :-
- Genetic drift
- Migration
- Mutation
- Natural selection
Answer
(1) Genetic drift
Solution
As per NCERT, if the change in allele frequency occurs by chance, it is called genetic drift.
⇒ Its effect is most marked in small populations (e.g. founder effect), where chance alone can fix or eliminate an allele.
∵ Migration (gene flow), mutation and natural selection are not purely chance events of sampling, they are not the answer.
∴ The chance change in allele frequencies is genetic drift.
Answer: (1)