➢What is the significance of the population’s size?
➢Has the genetic composition of the population changed over time—that is, has it evolved?
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➢These and other questions about the genetic
that occur in the genetic makeup of a
population because of systematic and random
evolutionary forces.
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内容
➢We shall investigate how these forces— mutation, migration, selection, and random genetic drift—shape the genetic composition of a population.
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➢The theory of population genetics is a theory
of allele frequencies.
➢Each gene in the genome exists in different
allelic states, and, if we focus on a particular
➢Did any of the genes mutate as they were transmitted through time?
➢How did migration to and from the island affect its genetic composition?
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➢Has the island’s genetic diversity increased, decreased, or remained the same?
gene, a diploid individual is either a
homozygote or heterozygotes.
➢Within a population of individuals, we can
calculate the frequencies of the different types
makeup and history of the people on Pitcairn
Island fall within the purview of population
genetics, a discipline that studies genes in
groups of individuals.
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A Remote Colony
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➢Which of the founding genes were passed down through time?
➢How did factors such as the health, vigor, and reproductive ability of the people, and the ways in which they chose mates, influence the pathways of genetic descent?
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1. Estimating Allele Frequencies
➢Because an entire population is usually too large to study, we resort to analyzing a representative sample of individuals from it.
➢We begin with an introduction to the basic methods of population genetic analysis.
➢As we shall see, these methods focus on the frequencies of the alleles that are present in the members of the population.
➢Population genetics examines allelic variation
among individuals, the transmission of allelic
variants from parents to offspring generation
after generation, and the temporal changes
Chapter 11 Population Genetics
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Chapter Outline
➢The Theory of Allele Frequencies ➢Natural Selection ➢Random Genetic Drift ➢Populations in Genetic Equilibrium
of a gene, and from these frequencies we can
estimate the frequency of each of the gene’s
Hale Waihona Puke alleles.➢These calculations are the foundation for
population genetics theory.
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Section 1 The Theory of Allele
Frequencies
➢ When the members of a population mate randomly, it is easy to predict the frequencies of the genotypes from the frequencies of their constituent alleles.