Q.36 Which of the following statement(s) about the effect of genetic drift is/are
correct?
(A) It can cause changes in the frequency of alleles at random
(B) It is a mechanism of evolution
(C) It can lead to loss of genetic variation within small populations
(D) It is significant in large populations
Correct answer: A, B, and C
Genetic drift causes random changes in allele frequencies and serves as a key evolutionary mechanism, particularly affecting small populations by reducing genetic variation. Option D is incorrect as its effects are minimal in large populations.
Option Analysis
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(A) Correct: Genetic drift produces random fluctuations in allele frequencies due to chance events like sampling error during reproduction.
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(B) Correct: Genetic drift qualifies as a mechanism of evolution alongside natural selection, mutation, and gene flow, driving changes in populations over generations.
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(C) Correct: In small populations, genetic drift accelerates the loss of alleles and heterozygosity, diminishing genetic variation and increasing fixation risk.
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(D) Incorrect: Genetic drift proves negligible in large populations where random events average out, unlike in small groups where effects dominate.
Introduction
The effect of genetic drift refers to random changes in allele frequencies driven by chance, serving as a core mechanism of evolution that profoundly impacts small populations by causing loss of genetic variation. In CSIR NET Life Sciences exams like Q.36, recognizing these effects distinguishes correct statements (A, B, C) from incorrect ones (D, where large populations minimize drift).
Core Effects
Genetic drift operates through sampling error, where allele transmission varies unpredictably across generations.
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Random shifts in allele frequencies occur without adaptive direction, as seen in bottleneck or founder events.
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As an evolution mechanism, it contributes to speciation and divergence alongside selection forces.
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Small populations suffer rapid genetic variation loss, elevating inbreeding and extinction risks.
CSIR NET Relevance
For CSIR NET aspirants focusing on evolutionary biology, genetic drift exemplifies microevolutionary change. Practice questions test its random nature versus selection’s directionality, with drift dominating in small, isolated groups—critical for ecology and conservation modules.
