Non-Mendelian and Cytoplasmic Inheritance in Genetics

Population genetics

The study of genetic variation within populations and how it changes across generations.

Gene pool

All the alleles of every gene in a population; only individuals that reproduce contribute to the next generation's gene pool.

Population

A group of individuals of the same species that occupy the same area and can interbreed.

Local population

A smaller subgroup within a species that breeds more frequently within itself than with the general population.

Polymorphism

The occurrence of two or more alleles that influence phenotype in a population.

Polymorphic gene

A gene that exists as two or more common alleles in a population.

Monomorphic gene

A gene that exists predominantly as a single allele in a population.

Single-nucleotide polymorphism (SNP)

A variation in a single base pair in the DNA sequence; accounts for most genetic variation among individuals.

Allele frequency

The proportion of a specific allele among all alleles for a given gene in a population.

Genotype frequency

The proportion of individuals with a specific genotype in a population.

Hardy-Weinberg equilibrium (HWE)

A condition where allele and genotype frequencies remain constant over generations in the absence of evolutionary forces.

Hardy-Weinberg equation

p² + 2pq + q² = 1, where p and q represent allele frequencies and genotype frequencies can be calculated from them.

HWE assumptions

No mutations, no genetic drift, no migration, no natural selection, and random mating.

Microevolution

Small-scale genetic changes in a population's gene pool across generations.

Mutation

A random change in DNA sequence that introduces new genetic variation into a population.

Genetic drift

Random changes in allele frequencies due to chance, especially in small populations.

Bottleneck effect

A sharp reduction in population size due to environmental events, leading to reduced genetic variation.

Founder effect

Occurs when a small group breaks off from a larger population to form a new one with limited genetic variation.

Natural selection

The process where individuals with advantageous traits have higher reproductive success, changing allele frequencies over time.

Fitness (Darwinian fitness)

The relative likelihood that a genotype will survive and reproduce, contributing to the next generation's gene pool.

Directional selection

Favors one extreme phenotype that is better adapted to the environment.

Balancing selection

Maintains two or more alleles in a population; includes heterozygote advantage.

Heterozygote advantage

When heterozygous individuals have higher fitness than either homozygote (e.g., sickle cell trait in malaria regions).

Negative frequency-dependent selection

Rare genotypes have higher fitness than common ones, maintaining genetic diversity.

Disruptive (diversifying) selection

Favors multiple distinct phenotypes, often in populations living in diverse environments.

Stabilizing selection

Favors intermediate phenotypes while selecting against extremes, reducing genetic variation.

Migration

The movement of individuals (and their alleles) between populations, altering allele frequencies.

Gene flow

The transfer of alleles from one population to another through migration.

Assortative mating

Nonrandom mating where individuals choose partners based on phenotype.

Positive assortative mating

Individuals mate with others of similar phenotype.

Negative assortative mating

Individuals mate with others of dissimilar phenotype.

Inbreeding

Mating between genetically related individuals; increases homozygosity and can cause inbreeding depression.

Outbreeding

Mating between genetically unrelated individuals; increases heterozygosity.

Inbreeding coefficient (F)

The probability that two alleles in an individual are identical by descent from a common ancestor.

Inbreeding depression

Reduced biological fitness in a population due to increased homozygosity for deleterious alleles.

Mutation rate

The probability that a gene will be altered by a new mutation per generation.

Gene flow (migration)

Movement of alleles between populations that reduces genetic differences and increases diversity.