Book contents
- Frontmatter
- Contents
- Preface
- Acknowledgments
- Chapter 1 Life Forms and Their Origins
- Chapter 2 Nucleic Acids
- Chapter 3 Proteins
- Chapter 4 Simple Chromosomes
- Chapter 5 Chromosomes of Eukarya
- Chapter 6 Genome Content
- Chapter 7 RNA Synthesis 1: Transcription
- Chapter 8 RNA Synthesis 2: Processing
- Chapter 9 Abundance of RNAs in Bacteria
- Chapter 10 Abundance of RNAs in Eukarya
- Chapter 11 Protein Synthesis
- Chapter 12 DNA Replication
- Chapter 13 Chromosome Replication
- Chapter 14 Molecular Events of Recombination
- Chapter 15 Micromutations
- Chapter 16 Repair of Altered DNA
- Chapter 17 Reproduction of Bacteria
- Chapter 18 Horizontal Gene Transfer in Bacteria
- Chapter 19 Cell Cycles of Eukarya
- Chapter 20 Meiosis
- Chapter 21 Chromosomal Abnormalities
- Chapter 22 Life Cycles of Eukarya
- Chapter 23 Reproduction of Viruses
- Chapter 24 Genetic Processes in Development
- Chapter 25 Sex Determination and Dosage Compensation
- Chapter 26 Cancer
- Chapter 27 Cutting, Sorting, and Copying DNA
- Chapter 28 Genotyping by DNA Analysis
- Chapter 29 Genetically Engineered Organisms
- Chapter 30 Genomics
- Chapter 31 Behavior of Genes and Alleles
- Chapter 32 Probability and Statistics Toolkit
- Chapter 33 Genes, Environment, and Interactions
- Chapter 34 Locating Genes
- Chapter 35 Finding and Detecting Mutations
- Chapter 36 Cytoplasmic Inheritance
- Chapter 37 Genetic Variation in Populations
- Chapter 38 Mutation, Migration, and Genetic Drift
- Chapter 39 Natural Selection
- Chapter 40 Quantitative Genetics
- Chapter 41 Speciation
- Chapter 42 Molecular Evolution and Phylogeny
- Glossary
- Index
Chapter 39 - Natural Selection
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- Acknowledgments
- Chapter 1 Life Forms and Their Origins
- Chapter 2 Nucleic Acids
- Chapter 3 Proteins
- Chapter 4 Simple Chromosomes
- Chapter 5 Chromosomes of Eukarya
- Chapter 6 Genome Content
- Chapter 7 RNA Synthesis 1: Transcription
- Chapter 8 RNA Synthesis 2: Processing
- Chapter 9 Abundance of RNAs in Bacteria
- Chapter 10 Abundance of RNAs in Eukarya
- Chapter 11 Protein Synthesis
- Chapter 12 DNA Replication
- Chapter 13 Chromosome Replication
- Chapter 14 Molecular Events of Recombination
- Chapter 15 Micromutations
- Chapter 16 Repair of Altered DNA
- Chapter 17 Reproduction of Bacteria
- Chapter 18 Horizontal Gene Transfer in Bacteria
- Chapter 19 Cell Cycles of Eukarya
- Chapter 20 Meiosis
- Chapter 21 Chromosomal Abnormalities
- Chapter 22 Life Cycles of Eukarya
- Chapter 23 Reproduction of Viruses
- Chapter 24 Genetic Processes in Development
- Chapter 25 Sex Determination and Dosage Compensation
- Chapter 26 Cancer
- Chapter 27 Cutting, Sorting, and Copying DNA
- Chapter 28 Genotyping by DNA Analysis
- Chapter 29 Genetically Engineered Organisms
- Chapter 30 Genomics
- Chapter 31 Behavior of Genes and Alleles
- Chapter 32 Probability and Statistics Toolkit
- Chapter 33 Genes, Environment, and Interactions
- Chapter 34 Locating Genes
- Chapter 35 Finding and Detecting Mutations
- Chapter 36 Cytoplasmic Inheritance
- Chapter 37 Genetic Variation in Populations
- Chapter 38 Mutation, Migration, and Genetic Drift
- Chapter 39 Natural Selection
- Chapter 40 Quantitative Genetics
- Chapter 41 Speciation
- Chapter 42 Molecular Evolution and Phylogeny
- Glossary
- Index
Summary
Overview
Natural selection is differential reproduction of genotypes in the absence of human intervention. The relative reproductive ability of a genotype is its fitness. Selection is a potentially strong force that can change both the population mean and its genetic variation; it is the principal agent of directional genetic change. The speed of evolution under natural selection is a function of fitness and allele frequencies. Rare deleterious alleles are eliminated very slowly from a population. One way genetic variation is maintained in a population is balancing selection, which favors heterozygotes.
Kinds of Selection
Selection occurs whenever one genotype reproduces at a higher or lower rate than other genotypes, on average, causing that genotype to contribute more or fewer copies of its genes to the population than other genotypes do. For example, a recessive lethal allele that acts at a prereproductive stage will be selected against because homozygotes will die before they can reproduce. Selection acts on all life forms, regardless of the mode of reproduction or the nature of the life cycle. It is the principal driving force of evolution. The speed of selection and its effect on equilibrium frequencies of alleles and genotypes can be quantified. Selection that acts on survival, fertility, and fecundity is called natural selection, while selection that acts on the mating success of sexual organisms is called sexual selection.
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- Information
- Fundamental Genetics , pp. 374 - 382Publisher: Cambridge University PressPrint publication year: 2004