Population Genetics and Hardy-Weinberg Equilibrium

Vocabulary flashcards covering the concepts, assumptions, and mathematical equations of population genetics and Hardy-Weinberg equilibrium.

Population

The biological unit where evolution actually occurs across generations, in contrast to individuals, which are subjected to natural selection.

Selection

Pressure imposed by the environment on individuals in the form of survival and reproductive success.

Adaptation

The evolutionary process whereby more fit individuals pass on heritable traits, making the next generation better suited to their environment.

Hardy-Weinberg Equilibrium as a Null Hypothesis

A mathematical baseline predicting what allele and genotype frequencies would look like if a population were left alone with no evolutionary forces or fitness differences acting on it.

Infinitely Large Population Assumption

The condition of Hardy-Weinberg equilibrium stating that the population must be large enough to prevent random sampling fluctuations and genetic drift from shifting allele frequencies.

No Natural Selection Assumption

The condition of Hardy-Weinberg equilibrium requiring that genotypes do not confer any fitness advantage or survival difference over one another.

No Mutation Assumption

The condition of Hardy-Weinberg equilibrium specifying that alleles do not randomly change from one form into another.

Random Mating Assumption

The condition of Hardy-Weinberg equilibrium requiring individuals to pair without preference, meaning sexual selection is absent.

No Migration Assumption

The condition of Hardy-Weinberg equilibrium requiring that gene flow does not occur via individuals introducing or removing alleles across populations.

Genetic Drift

Random fluctuations or loss of allele frequencies across generations resulting from small sample size rather than fitness advantages.

Allele Equation

The equation $p + q = 1$, which states that the sum of the probabilities of all alleles in a two-allele system must equal one.

Genotype Equation

The binomial expansion $p^2 + 2pq + q^2 = 1$, which calculates the expected frequencies of the three possible genotypes in a two-allele system at equilibrium.

$$p^2$$

The expected frequency of individuals homozygous for the first allele in a two-allele Hardy-Weinberg system.

$$2pq$$

The expected frequency of heterozygous individuals carrying one of each allele in a two-allele Hardy-Weinberg system.

$$q^2$$

The expected frequency of individuals homozygous for the second allele in a two-allele Hardy-Weinberg system.

Deviation from Hardy-Weinberg Equilibrium

A condition in which observed genotype frequencies differ from expected equilibrium frequencies, providing measurable evidence that evolution is actively occurring.