Lecture 3-Population Genetics Flashcards
Do populations evolve?
Populations evolve, not individuals. Natural selection acts on individuals but only the population evolves.
What is a population?
Group of individuals interbreeding and producing fertile offspring.
Sources of genetic variation?
- Sexual reproduction: Recombination of alleles (independent assortment)
- Mutations: Rare variations of alleles mostly in somatic cells (not passed down)
What are allele frequencies?
Every allele has a frequency in a population. # of alleles=Individuals x2, in diploid organisms.
Equations for allele frequencies?
Frequency must add to 1:
p+q=1
p=dominant, q=recessive
Hardy-weinberg used to calculate expected frequency:
p^2+2pq+q^2=1
what is the Hardy-Weinberg Principle
Frequencies remain constant from generation to genertation. The equation descrobes a non-evolving population
what are the 5 conditions of a non-evolving population?
- No mutations
- Random Mating
- Large Population
- No gene flow
- No natural selection
What is directional selection?
Extreme phenotype is favoured
What is disruptive selection?
Phenotypic extremes favored
What is stabilizing selection?
Intermediate phenotypes favored
What is genetic drift?
Chance change in allele frequencies that reduces variation.
What is the founder effect?
A small amount of individuals isolated from larger population form new population but with (usually) less diversity.
What is gene flow?
Movement of alleles among populations due to movement of fertile individual or gametes.
Effects of gene flow?
Greater variation in single population but less interpopulation variation.
