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

Problem 7

Chapter 20, Problem 7

Over the course of many generations in a small population, what effect does random genetic drift have on allele frequencies?

Verified step by step guidance

Understand that genetic drift is a mechanism of evolution that refers to random changes in the frequency of alleles in a population.

Recognize that in small populations, genetic drift has a more pronounced effect because random events can lead to significant changes in allele frequencies from one generation to the next.

Consider that over many generations, genetic drift can lead to the fixation or loss of alleles, meaning that an allele can become the only allele present in the population or be completely lost.

Acknowledge that genetic drift can reduce genetic variation within a population, as alleles are lost or fixed over time.

Note that genetic drift can lead to different populations diverging genetically from each other, especially if they are isolated, as random changes in allele frequencies accumulate over generations.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Random Genetic Drift

Random genetic drift is a mechanism of evolution that refers to random fluctuations in allele frequencies within a population due to chance events. In small populations, these random changes can lead to significant shifts in genetic variation over generations, potentially resulting in the loss of alleles or fixation of certain alleles, regardless of their adaptive value.

Allele Frequencies

Allele frequencies represent the proportion of different alleles of a gene in a population. They are crucial for understanding genetic diversity and evolution, as changes in these frequencies can indicate how populations evolve over time. In the context of random genetic drift, allele frequencies can change unpredictably, leading to reduced genetic variation.

Population Size and Genetic Drift

The size of a population significantly influences the impact of random genetic drift. In smaller populations, the effects of drift are more pronounced, leading to greater fluctuations in allele frequencies. This can result in rapid evolutionary changes, whereas larger populations tend to buffer against such random changes, maintaining more stable allele frequencies over time.

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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.

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Carl Linnaeus, the 18th-century botanist who laid the foundation for the modern system of taxonomic nomenclature, placed chimpanzees and humans in the same genus. Discuss the merits of this classification.

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Catastrophic events such as loss of habitat, famine, or overhunting can push species to the brink of extinction and result in a genetic bottleneck. What happens to allele frequencies in a species that experiences a near-extinction event, and what is expected to happen to allele frequencies if the species recovers from near extinction?

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Describe how selection at a locus can result in a loss of polymorphism surrounding the locus.