Topic 5 Bisc 102

Gene pool

All the genes (alleles) present in a population at a given time

Allele frequency

Proportion of a specific allele in the gene pool

Genotype frequency

Proportion of a specific genotype in a population

Microevolution

Change in allele frequencies within a population over time

Macroevolution

Large

Population

Group of individuals of the same species living in the same area at the same time

Hardy

Weinberg equilibrium

Hardy

Weinberg equation

p

Frequency of dominant allele in a population

q

Frequency of recessive allele in a population

Conditions for HWE

No selection, no mutation, no migration, random mating, large population

Null model

A baseline assumption that no evolutionary forces are acting

Selection

Differential survival and reproduction based on heritable traits

Genetic drift

Random changes in allele frequencies, strongest in small populations

Founder effect

When a new population starts from a small group with different allele frequencies

Bottleneck effect

Sharp reduction in population size causing loss of genetic variation

Gene flow

Movement of alleles between populations through migration

Mutation

Random change in DNA that creates new alleles

Point mutation

Change in a single base pair of DNA

Chromosomal mutation

Large

Somatic mutation

Mutation in body cells that is not inherited

Germline mutation

Mutation in reproductive cells that can be inherited

Directional selection

Selection that shifts trait distribution toward one extreme

Stabilizing selection

Selection that reduces variation around the average phenotype

Disruptive selection

Selection that favours both extremes over intermediate phenotypes

Balancing selection

Maintains multiple alleles in a population

Heterozygote advantage

Heterozygotes have higher fitness than either homozygote

Frequency

dependent selection

Fitness

Relative reproductive success of an individual

Adaptation

Heritable trait that increases fitness in a specific environment

Natural selection

Process where individuals with advantageous traits leave more offspring

Allele frequency change

Evidence that evolution is occurring

Equilibrium population

Population where allele frequencies remain constant over time

Disequilibrium population

Population where allele frequencies are changing

Expected genotype frequencies

p², 2pq, q² under Hardy

Observed frequencies

Actual measured genotype proportions in a population

Evolution

Change in allele frequencies over time

Random mating

Individuals pair without regard to genotype or phenotype

Large population assumption

Prevents random fluctuations in allele frequencies

No migration assumption

Prevents allele changes from movement between populations

No mutation assumption

Prevents introduction of new alleles

No selection assumption

All genotypes have equal reproductive success

Adaptive evolution

Evolution driven by natural selection

Non

adaptive evolution

Allele

Different version of a gene

Genotype

Genetic makeup of an organism

Phenotype

Observable traits of an organism

Sexual selection

Selection based on mating success

Convergent evolution

Independent evolution of similar traits in different lineages

Lactase persistence

Ability to digest lactose into adulthood due to genetic variation

Skin colour adaptation

Evolution driven by UV radiation, vitamin D, and folate balance