Lecture 7 - Population Genetics Part 2

What five conditions are required for Hardy–Weinberg equilibrium?

no mutations, random mating, no natural selection, very large population, no gene flow

What can happen when a population does not meet Hardy–Weinberg conditions?

allele or genotype frequencies may change

What is non-random mating?

when individuals do not mate randomly in a population

How does outbreeding affect genetic variation?

promotes genetic variability

How does inbreeding affect a population?

increases homozygosity, reduces genetic variation

Why can inbreeding increase the risk of recessive conditions?

related individuals more likely to carry the same recessive allele

Does inbreeding alone change allele frequencies?

no, mainly changes genotype frequencies

What is natural selection?

individuals with traits that improve survival or reproduction tend to leave more offspring

How does natural selection change allele frequencies?

better alleles can become more common over generations

What is genetic drift?

random changes in allele frequencies caused by chance events

In which populations does genetic drift have the greatest effect?

small populations

What are the main effects of genetic drift?

loss of genetic variation, random changes in allele frequencies, fixation of harmful alleles

What is allele fixation?

when an allele reaches a frequency of 1, only allele remaining at the locus

What is the founder effect?

small group establishes a new population with only some of original populations alleles

How does the founder effect affect genetic variation?

some alleles lost, others more common by chance

What is a population bottleneck?

drastic reduction in population size

How does a population bottleneck affect allele frequencies?

surviving individuals may carry alleles more frequently, some alleles disappear

What is gene flow?

movement of alleles between populations through individuals or their gametes

How does gene flow affect differences between populations?

reduces genetic differences between populations

How can gene flow affect genetic variation within a population?

can introduce new alleles and increase genetic variation

What can happen when gene flow between populations is extensive?

populations may combine into a single gene pool