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

Sanders - Genetic Analysis: An Integrated Approach 3rd Edition

Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook

Sanders 3rd Edition

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

Problem 13c

Chapter 20, Problem 13c

Two populations of deer, one of them large and living in a mainland forest and the other small and inhabiting a forest on an island, regularly exchange members that migrate across a land bridge that connects the island to the mainland. In which population do you expect to see the greatest allele frequency change? Why?

Verified step by step guidance

Understand the concept of allele frequency: Allele frequency refers to how common a particular allele is in a population. It is influenced by factors such as genetic drift, migration, mutation, and natural selection.

Recognize the role of population size: Genetic drift, which is the random change in allele frequencies, has a stronger effect in smaller populations because random events can disproportionately impact the gene pool.

Consider the impact of migration: Migration introduces new alleles into a population or removes alleles from it, altering allele frequencies. The smaller population is more likely to experience significant changes due to the influx or outflow of alleles.

Analyze the scenario: The island population is smaller, so genetic drift and migration will have a greater impact on its allele frequencies compared to the larger mainland population. The larger population is more stable and less susceptible to random changes.

Conclude the reasoning: The greatest allele frequency change is expected in the smaller island population because it is more affected by genetic drift and migration due to its size and limited genetic diversity.

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Key Concepts

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

Genetic Drift

Genetic drift refers to the random fluctuations in allele frequencies within a population, particularly in small populations. In smaller populations, such as the island deer, random events can have a more significant impact on allele frequencies, leading to greater changes over time compared to larger populations.

Gene Flow

Gene flow is the transfer of genetic material between populations through migration. In this scenario, the exchange of deer between the mainland and island populations can introduce new alleles to each population, potentially altering allele frequencies. The extent of gene flow can influence genetic diversity and adaptation in both populations.

Population Size and Allele Frequency Change

The size of a population plays a crucial role in how allele frequencies change over time. Larger populations tend to maintain stable allele frequencies due to the buffering effect of a greater number of individuals, while smaller populations are more susceptible to rapid changes in allele frequencies due to genetic drift and the effects of inbreeding.

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Related Practice

Textbook Question

Look over the 10 diseases approved for genetic health risk assessment listed in Application Chapter B. Select one disease other than the three discussed in Application Chapter B or in this chapter (alpha-1 antitrypsin deficiency, late-onset Alzheimer disease, and celiac disease) or another of the diseases of your choice. Do a brief Internet search to find and download (1) one article for a nonscientific audience identifying the gene or genes whose alleles are associated with occurrence of the disease and (2) one scientific paper that provides data supporting the association of specific alleles of the gene or genes with the disease. Write a short summary combining the information contained in the two papers.

Textbook Question

Two populations of deer, one of them large and living in a mainland forest and the other small and inhabiting a forest on an island, regularly exchange members that migrate across a land bridge that connects the island to the mainland. If you compared the allele frequencies in the two populations, what would you expect to find?

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Textbook Question

Two populations of deer, one of them large and living in a mainland forest and the other small and inhabiting a forest on an island, regularly exchange members that migrate across a land bridge that connects the island to the mainland. An earthquake destroys the bridge between the island and the mainland, making migration impossible for the deer. What do you expect will happen to allele frequencies in the two populations over the following 10 generations?

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Textbook Question

Directional selection presents an apparent paradox. By favoring one allele and disfavoring others, directional selection can lead to fixation (a frequency of 1.0) of the favored allele, after which there is no genetic variation at the locus, and its evolution stops. Explain why directional selection no longer operates in populations after the favored allele reaches fixation.

Textbook Question

The mtDNA sequence of Neanderthals is more similar to that of modern humans than to that of Denisovans. However, analyses of nuclear DNA clearly indicate that Neandertals and Denisovans share a more recent common ancestor than either of these hominins shares with modern humans. Propose a hypothesis to resolve the discrepancy between the mtDNA and the nuclear genome.

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Textbook Question

What is inbreeding depression? Why is inbreeding depression a serious concern for animal biologists involved in species-conservation breeding programs?