NEET · Biology · STD 12 - 6. evolution

Random unidirectional change in allele frequencies that occurs by chance in all populations and especially in small populations is known as

A migration
B natural selection
C genetic drift
D mutation.

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Answer & Solution

Correct Answer

(C) genetic drift

Step-by-step Solution

Detailed explanation

(c) : Genetic drift (Sewall Wright effect) is the random change in the frequency of alleles in a population over successive generations in the gametes. Each new generation differs from its parental generation with regard to allele frequencies simply because of random variation in the distribution of gametes. This process is more rapid in smaller populations, or when the alleles concerned confer no apparent benefit compared to their counterparts.

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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