Textbook Question
Identify and describe the evolutionary forces that can cause allele frequencies to change from one generation to the next.
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Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172
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Table of contents
- Ch. 1 - The Molecular Basis of Heredity, Variation, and Evolution64
- Ch. 2 - Transmission Genetics144
- Ch. 3 - Cell Division and Chromosome Heredity81
- Ch. 4 - Gene Interaction87
- Ch. 5 - Genetic Linkage and Mapping in Eukaryotes103
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages73
- Ch. 7 - DNA Structure and Replication71
- Ch. 8 - Molecular Biology of Transcription and RNA Processing79
- Ch. 9 - The Molecular Biology of Translation110
- Ch. 10 - Eukaryotic Chromosome Abnormalities and Molecular Organization100
- Ch. 11 - Gene Mutation, DNA Repair, and Homologous Recombination86
- Ch. 12 - Regulation of Gene Expression in Bacteria and Bacteriophage90
- Ch. 13 - Regulation of Gene Expression in Eukaryotes38
- Ch. 14 - Analysis of Gene Function via Forward Genetics and Reverse Genetics72
- Ch. 15 - Recombinant DNA Technology and Its Applications69
- Ch. 16 - Genomics: Genetics from a Whole-Genome Perspective49
- Ch. 17 - Organelle Inheritance and the Evolution of Organelle Genomes27
- Ch. 18 - Developmental Genetics43
- Ch. 19 - Genetic Analysis of Quantitative Traits66
- Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels105
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
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Sanders 3rd EditionCh. 20 - Population Genetics and Evolution at the Population, Species, and Molecular LevelsProblem 6
Sanders 3rd EditionCh. 20 - Population Genetics and Evolution at the Population, Species, and Molecular LevelsProblem 6Chapter 20, Problem 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.
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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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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
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.
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Genetic Drift
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.
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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.
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Related Practice
Textbook Question
Describe how natural selection can produce balanced polymorphism of allele frequencies through selection that favors heterozygotes.
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Textbook Question
Thinking creatively about evolutionary mechanisms, identify at least two schemes that could generate allelic polymorphism in a population. Do not include the processes described in the answer to Problem 4.
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Textbook Question
Over the course of many generations in a small population, what effect does random genetic drift have on allele frequencies?
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Textbook Question
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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Textbook Question
George Udny Yule was wrong in suggesting that an autosomal dominant trait like brachydactyly will increase in frequency in populations. Explain why Yule was incorrect.
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