Topic 14 pt 1: Population Genetics Flashcards
In population genetics we study the distribution of genetic variation…
Within and between populations of species
Measure genetic variation within populations by calculating…
Allele frequencies, genotype frequencies, heterozygozity
Evolution happens at the
population level
Evolution definition from a genetics view
changes in allele frequencies form one generation to the next within a population
How do we calculate genotypic frequencies
Number of individuals with the genotype divided by total number of individuals in sample
f(AA) = #AA individuals / N
Slide 8
Genotype frequency calculations ex
How do we calculate allelic frequency
Number of copies of a particular allele present in a sample divided by total number of alleles
Freq of allele = #copies of alleles / # copies of all alleles at locus in a pop
What are p and q
p = freq of allele one
q = freq of allele two
p + q = 1
p =
p = 2(nAA) + (nAa) / 2ntotal
Slides 10, 11
Allelic freq calculation
What is the Hardy-Weinberg equation? What does it model
p^2 + 2pq + q^2 = 1
Models genotype freqs from one generation to the next in absence of evolutionary forces
What remains constant in the absence of evolution
Amount of genetic variation in a randomly mating population over generations
Assumptions of the Hardy-Weinberg principle
- Individuals have to be randomly mating
- Infinitely large population -> no genetic drift
- No new mutations
- No migration
- No selection -> natural selection
Four forces of evolution
Genetic drift, migration, mutation, natural selection
Predictions of HWE
- Allelic freqs of pop do not change
- Genotypic freqs stabilize after one generation in proportions p2 + 2pq + p2 =1
