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Chapter 20 Genes within Populations
Gene- section of DNA that codes for or regulates a protein (of subsequent product)
Mutation- Change in DNA sequence
Allele- version of a gene (sometimes dominant or recessive)
Dominant- expressed when at least 1 copy is present
Recessive- must be 2 copies to be expressed
Homozygous- both alleles are the same
Heterozygous- the alleles are different
Locus (loci) - physical location of a gene on a chromosome
Genetic Variation and Evolution
Genetic variation
Differences in alleles of genes found within individuals in a population
Raw material for natural selection
Evolution
How an entity changes through time
Development of modern concept traced to Darwin
-“Descent with modification”
Population genetics
Study of properties of genes in a population
Evolution results in a change in the genetic composition of a population
Genetic variation is the raw material for selection
In nature, genetic variation is the rule
Polymorphic loci
More than one allele at frequencies greater than mutation alone
Heterozygosis
Probability that a randomly selected gene will be heterozygous in a randomly selected individual
Hardy-Weinberg principle
Hardy-Weinberg equilibrium
Proportions of genotypes do not change in a population if
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No genes are transferred to or from other sources (no immigration or emigration
takes place)
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The population size is very large
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