Hardy-Weinberg equations
p^2 + 2pq + q^2 = 1
or (p+q)^2 = 1
and
p+q=1
Hardy-Weinberg assumptions
- population size is infinite
- random mating occurs
- natural selection does not operate
- migration does not introduce new alleles
- no genetic drift
Effect of directional selection on allele and gene frequencies
frequencies of one allele will increase
Effect of mutation on genetic variation
more diversity
Effect of recombination on genetic variation
diversity
Effect of natural selection on genetic variation
increase or decrease an allele or genotype
Effect of genetic drift on genetic variation
chance fluctuations of allele frequencies, especially prominent in small populations
Effect of gene flow on genetic variation
can introduce novel alleles, increase frequency of existing alleles, remove/reduce existing alleles, and create a mixed population
What is the relationship between mutation and selection in a population?
if there are more new mutations, the harmful allele will be more common. If there is stronger selection against the mutation, the harmful allele will be less common
To find the new migrant population for random mating
pN = (1-m) (pI) + m(pC)
m = migrant fraction = nC/total population
nI = initial population
nC = number of migrants
pI = initial island p
pC = admixed p
Inbreeding
mating between related individuals. does not affect allele frequencies, but redistributes them to favour homozygosity
Allopatric speciation
Populations diverge due to physical barrier and thus new species develop in separate geographic locations
sympatric speciation
Populations share a territory but are isolated by genetic, behavioural, seasonal or ecosystem-based mechanisms that prevent gene flow
hybrid speciation
Formation of new speciation due to hybridization between existing species
