Trait Variation: Hardy-Weinberg, allele frequencies (exam 2)

When could you say that evolution has occurred?

If allele frequencies change between generations

What mechanisms cause evolution?

-natural selection

-mutations

-genetic drift

-gene flow

Define natural selection

Natural selection is the process by which individuals with advantageous heritable traits survive and reproduce more successfully than others, causing those traits to become more common in the population over generations.

Define genetic drift

Random changes in allele frequencies caused by chance; not related to fitness

-genetic drift is strongest in small populations

What is the bottleneck effect?

A random disaster kills many individuals. As a result, allele frequencies change randomly and genetic variation is reduced. Survivors may not represent the original population’s genetic diversity.

Define gene flow

the movement of alleles from one population to another through the migration of individuals

For a population to be in Hardy-Weinberg equilibrium, what assumptions must be true?

-Large Population; minimizes genetic drift

-Random mating

-No natural selection; all alleles have equal fitness

-No mutations; no new alleles arise

-No migration (gene flow); no alleles entering or leaving

-allele and genotype frequencies will stay the same if these conditions are met

Why does random mating matter?

Random mating is important because it prevents certain alleles or genotypes from being favored during reproduction, allowing genotype frequencies to remain stable from generation to generation.

What happens if mating is not random?

-Certain traits may become more or less common

-Can result in more homozygotes (AA or aa) and fewer heterozygotes

-Inbreeding may also occur, which reduced heterozygotes and increases homozygotes

What is the purpose of a chi-square test?

-Chi-square is used to determine whether a population is actually in Hardy-Weinberg equilibrium

How would you determine whether a population is in Hardy-Weinberg equilibrium?

-Use a chi-square test and compare the observed genotype frequencies to the expected genotype frequencies

What does it mean for a population to be hardy-Weinberg equilibrium?

It means that evolution is not occurring and as a result the allele frequencies are remaining constant from generation to generation.