Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels

Sanders - Genetic Analysis: An Integrated Approach 3rd Edition

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Sanders 3rd Edition

Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels

문제 6

20장, 문제 6

Genetic drift, an evolutionary process affecting all populations, can have a significant effect in small populations, even though its effect is negligible in large populations. Explain why this is the case.

검증된 단계별 안내

Understand that genetic drift refers to random changes in allele frequencies within a population due to chance events, rather than natural selection.

Recognize that in small populations, random sampling effects are more pronounced because each individual's genetic contribution represents a larger fraction of the gene pool.

Explain that because of this, alleles can become fixed (reach 100% frequency) or lost (0% frequency) more quickly in small populations purely by chance.

Contrast this with large populations, where the large number of individuals buffers against random fluctuations, making genetic drift's effect negligible.

Summarize that the impact of genetic drift is inversely related to population size because random events have a stronger influence when fewer individuals contribute genetically.

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Genetic Drift

Genetic drift is a random change in allele frequencies within a population due to chance events. It occurs independently of natural selection and can lead to the loss or fixation of alleles over time, especially in small populations.

Population Size and Genetic Variation

Population size influences the impact of genetic drift; in small populations, random fluctuations can drastically change allele frequencies, reducing genetic variation. In large populations, these random changes are diluted, making drift effects negligible.

Founder Effect and Bottleneck Effect

The founder effect and bottleneck effect are examples of genetic drift where small groups establish new populations or survive drastic reductions, respectively. Both lead to reduced genetic diversity and increased influence of random allele frequency changes.