Beyond Alleles – Quantitative Genetics and the Evolution of Phenotypes

These flashcards cover key terminology and concepts related to quantitative genetics and the evolution of phenotypes, as outlined in the lecture notes.

Phenotypic plasticity

The ability of a single genotype to produce multiple phenotypes depending on environmental conditions.

Broad sense heritability (H²)

Captures all sources of genetic variance, including additive effects, dominance effects, and epistasis.

Narrow sense heritability (h²)

Focuses only on additive genetic effects and is relevant for predicting evolutionary change.

Linkage disequilibrium (LD)

The nonrandom association of alleles at different loci, often due to their close physical proximity on a chromosome.

Quantitative trait loci (QTL)

Genetic regions associated with phenotypic variation, identified through mapping studies.

Directional selection

Favors individuals at one extreme of a trait distribution, causing the mean phenotype to shift.

Stabilizing selection

Favors individuals with trait values near the mean, reducing variance in the trait.

Disruptive selection

Favors both extremes over intermediate trait values, potentially leading to population divergence.

Variance (V)

A measure of how widely a trait varies within a population, comprising genetic and environmental components.

Parent-offspring regression

A method to estimate narrow sense heritability by measuring traits in both parents and their offspring.

Breeder's Equation

Predicts evolutionary response (R) as R=h²×S, where S is the selection differential.

Epistatic variance (V_I)

Results from gene interactions across loci, contributing to genetic variance measurements.

Genotype-by-environment interaction (V_G × E)

Occurs when different genotypes respond differently to environmental changes, indicating heritable plasticity.

Reaction norms

Graphs that depict how a genotype's phenotype changes in response to varying environmental conditions.

Quantitative genetics

A field that examines the genetic basis of phenotypic traits influenced by multiple genes and environmental factors.

Epistasis

Non-additive interactions between alleles at different loci that affect phenotype expression.

Dominance variance (V_D)

Arises from interactions between alleles at the same locus, contributing to overall genetic variance.

Linkage equilibrium

A state in which alleles at different loci assort independently, resulting in random mixing of alleles.

Genetic recombination

The process during meiosis that mixes alleles and can break linkage disequilibrium over generations.

Selection differential (S)

The difference between the mean trait value of selected individuals and the mean trait value of the broader population.

Genome-Wide Association Studies (GWAS)

Research methods that use natural variations in large populations to link genetic loci to specific traits.

Quantitative Trait Locus (QTL) Mapping

Method to determine the genetic basis of complex traits by correlating genetic markers with phenotype variation.

Genetic variance (V_G)

The component of total phenotypic variance attributable to differences in genotype among individuals.

Environmental variance (V_E)

The component of total phenotypic variance caused by environmental differences experienced by individuals.

Fitness

The reproductive success of an individual or phenotype in a specific environment.