Hardy Weinberg and Microevolution

Flashcards covering key concepts from lecture notes on Hardy Weinberg equations, microevolution, genetic drift, and related evolutionary forces and phenomena.

Hardy Weinberg Equations

Mathematical models designed to address the problem in Mendelian genetics where expected genotypic ratios often do not match real populations, assuming random mating and no evolutionary forces.

p

By convention, the proportion of dominant alleles in a population.

q

By convention, the proportion of recessive alleles in a population.

p + q = 1

The sum of the proportions of dominant (p) and recessive (q) alleles, representing 100% of the alleles for a given gene in a population.

p^2

The expected frequency of the homozygous dominant genotype in a population, according to Hardy Weinberg.

q^2

The expected frequency of the homozygous recessive genotype in a population, according to Hardy Weinberg.

2pq

The expected frequency of the heterozygous genotype in a population, according to Hardy Weinberg.

p^2 + 2pq + q^2 = 1

The sum of all possible genotype frequencies (homozygous dominant, heterozygous, homozygous recessive), representing 100% of the genotypes for a given gene in a population.

Evolutionary Force/Pressure

Factors that can cause allele frequencies in a population to change over time, violating Hardy Weinberg equilibrium.

Hardy Weinberg Equilibrium

A state in a population where allele frequencies are not expected to change over time, meaning the population is not currently evolving at a particular genetic locus.

Mutation

A change in the DNA sequence that can introduce new alleles into a population, thereby altering allele frequencies and violating Hardy Weinberg equilibrium; the only process that generates true new genetic variation.

Microevolution

Any change in allele frequencies in a population over time; the lowest level at which evolution can happen, occurring at the population level and, given enough time, can lead to larger-scale evolution (macroevolution).

Genetic Drift

Random fluctuations in allele frequencies that occur in populations, especially small ones, due to chance events in survival and reproduction (e.g., random variation in who lives, dies, or reproduces), leading to changes in allele frequencies that are independent of allele quality.

Fixation (Allelic/Genetic)

A phenomenon where one allele becomes 100% prevalent in a population, and all other alleles for that gene are lost, resulting in zero genetic variation at that locus.

Gene Flow (Migration)

The movement of alleles between populations, typically through the migration of individuals and their subsequent reproduction, which can reintroduce lost alleles into a population or alter existing allele frequencies.

Genetic Bottleneck

An extreme form of genetic drift that occurs when a population undergoes a drastic reduction in size over a short period, leading to a surviving population whose genetic makeup may not reflect the original larger population, often resulting in reduced genetic diversity.

Greater Prairie Chicken Example

A case study illustrating how habitat reduction led to a genetic bottleneck, severely decreasing genetic diversity and hatching success in Illinois populations compared to adjacent, unbottlenecked populations.