Stevies Lectures Flashcards
(38 cards)
What is the Hardy-Weinberg equilibrium?
A null model stating that allele frequencies will not change from one generation to the next if certain assumptions are met.
What are the five assumptions of the Hardy-Weinberg equilibrium?
No selection, no mutation, no migration, no genetic drift, and random mating.
Why is Hardy-Weinberg equilibrium important in studying evolution?
It provides a baseline to detect evolutionary change by comparing observed vs. expected allele/genotype frequencies.
How does selection impact allele frequencies?
It can increase or decrease the frequency of alleles depending on the type and direction of selection.
What is mutation–selection balance?
A state where the introduction of deleterious alleles by mutation is balanced by their removal by selection.
Why is mutation important despite being a weak force alone?
Mutation introduces new genetic variation, which is essential for evolution to occur.
How does migration affect allele frequencies?
It generally homogenizes allele frequencies among populations, preventing divergence.
How can migration maintain variation in a population?
It can oppose directional selection by reintroducing alleles that selection is removing.
What is genetic drift?
Random changes in allele frequencies due to chance, not selection.
Why is genetic drift stronger in small populations?
Smaller populations have more sampling error, so chance events have a bigger effect on allele frequencies.
What are the genetic consequences of genetic drift?
Loss of alleles, reduced heterozygosity, and reduced genetic diversity.
What is linkage disequilibrium (LD)?
A non-random association of alleles at different loci.
What creates LD in populations?
Physical linkage, multilocus selection, genetic drift, and population admixture.
How is LD eliminated?
Through recombination during sexual reproduction.
Why is measuring LD important?
It helps understand evolutionary processes and infer past selection or population history.
How can LD affect evolution?
Selection at one locus can indirectly affect allele frequencies at linked loci.
Why is sexual reproduction adaptive?
It reshuffles alleles, creating new combinations and increasing adaptability in changing environments.
What are quantitative traits?
Traits that show continuous variation and are influenced by multiple genes and the environment.
How do we partition phenotypic variation?
Into genetic (Vg) and environmental (Ve) components: Vp = Vg + Ve.
What is heritability (h²)?
The proportion of phenotypic variation due to genetic variation: h² = Vg / Vp.
How is the strength of selection measured?
By relating phenotype to fitness (e.g., using selection gradients or differentials).
How can we predict evolutionary response to selection?
Using the breeder’s equation: R = h² × S.
How do different selection patterns affect variation?
Directional reduces variation, stabilizing maintains mean but reduces extremes, disruptive increases variation by favoring extremes.
What is inbreeding?
Mating between relatives, leading to increased homozygosity by descent.
