L21 Population Genetics & Natural Selection

Vocabulary flashcards for Population Genetics & Natural Selection concepts.

Population

Localized group of individuals of the same species

Gene Pool

Total aggregate of genes (and their alleles) in the population at one time

Why we need to estimate genotype frequencies in population

To predict how many individuals will inherit genetic disease, and how many are carriers.

Hardy-Weinberg Equation

p² + 2pq + q² = 1; used to predict genotype frequencies in a population

Causes of change in allele frequency

Random genetic drift, mutation, gene flow/ migration, founder effect, bottleneck effect, natural selection or non-random mating.

Random Genetic Drift

A random change in allele frequencies due to sampling error over generations

Bottleneck Effect

Population reduction that results in loss of genetic diversity because when population increases again it will consist only of the remnants.

Founder Effect

Reduced genetic variation when a new population is founded by a small number of individuals

Stabilizing Selection

Natural selection that favors intermediate variants by acting against extreme phenotypes

Directional Selection

Natural selection that favors one extreme phenotype, causing a shift in the population's genetic variance toward that extreme over time.

Disruptive Selection

Natural selection that favors both extremes over intermediate phenotypes

Sexual Selection

Individuals with certain inherited characteristics are more likely than other individuals to obtain mates. (eg birds with long tails)

What type of selection is this?

Disruptive

Frequency-Dependent Selection

The fitness of a genotype is influenced by its frequency in a population. (how rare or common)

Spatial distribution of genetic variation (Cline)

The gradual geographical change in genetic/phenotypic composition.

Migration (Gene Flow)

Individual from one population mates with someone from another gene pool. New alleles, change in existing allele proportion and population size, makes populations more similar.

Mutation

A change in the nucleotide sequence of an organism's DNA, creating new alleles.