The Genetic Populations

Front 1

Assortative mating

Back 1

A mating pattern in which individuals with similar phenotypes or genotypes mate with one another. (p. 232)

Front 2

Balanced polymorphism

Back 2

A stable equilibrium in which more than one allele is present at a locus. (p. 221)

Front 3

Balancing selection

Back 3

Natural selection that leads to an intermediate phenotype or to a stable equilibrium in which more than one allele is present. See also balanced polymorphism. (p. 221)

Front 4

Directional selection

Back 4

A process of selection in which selection drives phenotype in a single direction, or in which selection drives allele frequencies in a single direction toward fixation of a favored allele. See also balancing selection. (p. 218)

Front 5

Disassortative mating

Back 5

A mating pattern in which individuals with dissimilar phenotypes or genotypes mate with one another. (p. 232)

Front 6

Fecundity

Back 6

A measure of the ability to produce offspring. (p. 227)

Front 7

Fixation

Back 7

In population genetics, an allele is said to go to fixation in a population when it replaces all alternative alleles at the same locus -- that is, when its frequency reaches 1. (p. 218)

Front 8

Frequency-dependent selection

Back 8

A form of selection in which the fitness associated with a trait or genotype is dependent upon the frequency of that trait or genotype in a population. (p. 224)

Front 9

Frequency-independent selection

Back 9

A form of selection in which the fitness associated with a trait is not directly dependent upon the frequency of that trait in a population. (p. 218)

Front 10

Hardy - Weinberg equilibrium

Back 10

Given a set of allele frequencies, the expected set of genotype frequencies that will be observed under the Hardy - Weinberg model. (p. 209)

Front 11

Hardy - Weinberg model

Back 11

A null model for how genotype frequencies relate to allele frequencies in large populations and how they change over time in the absence of these evolutionary processes: natural selection, mutation, migration, assortative mating, and genetic drift. (p. 208)

Front 12

Heterozygote advantage

Back 12

A form of frequency-independent selection in which heterozygote genotypes have higher fitness than the corresponding homozygote genotypes. (p. 221)

Front 13

Identical by descent

Back 13

When two or more gene copies are identical because of shared descent through a recent common ancestor. (p. 232)

Front 14

Inbreeding

Back 14

Mating with genetic relatives. (p. 232)

Front 15

Inbreeding depression

Back 15

A decrease in fitness that results from individuals mating with genetic relatives. See also inbreeding. (p. 235)

Front 16

Mutation - selection balance

Back 16

An equilibrium frequency of deleterious mutations in which these deleterious mutations are maintained at a positive frequency in a population due to a balance between ongoing deleterious mutation and the purging effect of natural selection. (p. 230)

Front 17

Overdominance

Back 17

A form of frequency-independent selection in which heterozygote genotypes have higher fitness than the corresponding homozygote genotypes. (p. 221)

Front 18

Population genetics

Back 18

A subdiscipline in evolutionary biology that investigates how allele frequencies and genotype frequencies change over time. (p. 206)

Front 19

Selection coefficient

Back 19

A measure of the strength of natural selection for or against a specific phenotype or genotype. (p. 217)

Front 20

Underdominance

Back 20

A form of frequency-independent selection in which the heterozygote genotype has a lower fitness than either corresponding homozygote genotype. (p. 222)

Front 21

Wright's F-statistic

Back 21

A statistical measure of the degree of homozygosity in a population. (p. 234)