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Following are key points about the effect of genetic drift :
(A) Genetic drift is significant in small populations.
(B) Genetic drift can cause allele frequencies to change in a pre-directed way.
(C) Genetic drift can lead to a loss of genetic variation within populations.
(D) Genetic drift can cause harmful alleles to become fixed.
Which one of the following combination of the above statements are true ?
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Eduncle Best Answer
Changes in relative allele frequency due only to random sampling error are known as genetic drift, a stochastic process. Hence Statement B is wrong. The smaller the population, the smaller the subset of potentially successful gametes, and the more likely that genetic drift will occur. Hence Statement A is right. Genetic drift can happen in two ways:
Founder Effect in which a small sample of breeding individuals from a large population colonizes a new area.
Bottleneck Effect: most members of a large population are removed (perhaps due to some natural disaster such as a hurricane, volcanic eruption, pathogen invasion or other catastrophe that doesn’t favor any particular genotype over another) leaving only a few survivors. Through sampling error, genetic drift can cause populations to lose genetic variation. Hence statement C is right. Alleles which are not harmful nor beneficial can become fixed by chance through genetic drift. In very small population genetic drift can cause alleles that are slightly harmful to become fixed. When this occurs the population’s survival can be threatened. Hence option D is right.