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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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 D.8
Sanders 3rd EditionCh. 20 - Population Genetics and Evolution at the Population, Species, and Molecular LevelsProblem D.8Chapter 20, Problem D.8
Describe how selection at a locus can result in a loss of polymorphism surrounding the locus.
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Understand that selection at a locus refers to the process where certain alleles increase in frequency because they confer a fitness advantage, while others decrease or are eliminated.
Recognize that when a beneficial allele is strongly favored by selection, it can rapidly increase in frequency and eventually become fixed in the population, meaning all individuals carry that allele.
Know that loci physically close to the selected locus on the chromosome tend to be inherited together due to linkage, a phenomenon called genetic hitchhiking or selective sweep.
Realize that as the beneficial allele rises to fixation, the linked alleles at nearby loci also increase in frequency, reducing genetic variation (polymorphism) in that surrounding region.
Conclude that this reduction in polymorphism occurs because recombination has limited opportunity to separate the beneficial allele from its neighboring alleles during the rapid selective sweep, leading to a loss of diversity around the selected locus.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Natural Selection and Selective Sweeps
Natural selection favors alleles that increase an organism's fitness, causing these alleles to rise in frequency. When a beneficial mutation at a locus rapidly increases in frequency, it can 'sweep' through the population, reducing genetic variation at nearby linked loci, a process known as a selective sweep.
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Natural Selection
Genetic Linkage and Linkage Disequilibrium
Genetic linkage refers to the physical proximity of genes on a chromosome, which affects their likelihood of being inherited together. Linkage disequilibrium occurs when alleles at different loci are non-randomly associated, so selection at one locus can indirectly reduce variation at linked loci.
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Polymorphism and Genetic Variation
Polymorphism is the presence of two or more alleles at a locus within a population. Genetic variation is essential for evolution, but strong selection at one locus can reduce polymorphism nearby by favoring one allele and eliminating others, leading to a loss of diversity in that genomic region.
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Related Practice
Textbook Question
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.
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?
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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Textbook Question
How can ancient DNA provide insight into past migrations that analyses of extant human genomes fail to uncover?
Textbook Question
Denisovans are known from bones found in Denisova Cave in the Altai Mountains in Siberia, but traces of their DNA are found in Australians and Melanesians, whose ancestors likely migrated across Asia much farther to the south. How can these geographic differences be reconciled?