Population Genetics (L19-21) Flashcards
Heterozygosity
frequency of heterozygotes
Genotype frequency
number of individuals with genotype/total individuals
So all frequencies add to 1
Allele frequency
Number of allele present/total allele
So all allele frequencies add to 1
Assumptions of population genetics
x 4
- diploid organisms
- Non-overlapping generations
- Autosomal loci
- Random mating
Hardy Weinberg assumptions - therefore some of the assumptions of population genetics
x 8
- Random mating
- No selection
- No migration
- No mutation
- Non-overlapping generations
- Autosomal locus
- Infinite population size
- Diploid organisms
Allele lottery
the idea that the allele frequency in next gen under genetic drift is going to be subject to stochastic sampling
Homozygosity
The frequency of homozygotes - tending to homozygosity means tending towards all being homozygotes
Using effective population size, what is a large population and what is a small population
large is Ne of >10,000
small is <100
genetic differentiation
a difference in allele frequency between subpopulations due to genetic drift causing allele frequency divergence
Wahlund effect
The deficiency of heterozygotes compared to HWE when summing across subpopulations
Fixation index
the proportional difference between expected heterozygosity in the total population and actual heterozygosity in total population
- also known as
proportion of genetic variance in subpop relative to total pop - level of inbreeding in subpop compared to total pop
Inbreeding
Homozygosity for alleles that are identical - by - descent (idb)
= autozygosity
What is F
The inbreeding coefficient = the probability that two randomly drawn alleles are ibd
mating system inbreeding
non-random mating among relatives, regardless of population size
What does μstand for?
the constant rate of mutation per locus per generation
What happens if fitness is random with respect to genotype?
No selection occurs
Absolute measurement of fitness
average total number of surviving offspring for a genotype
Relative fitness
fitness compared to another genotype - easiest to compare difference in fitness
What do we ignore when using relative fitness
changes in population size
2 different components of fitness
- survival to adulthood
2. fecundity
What is fecundity
the reproductive output of an individual
- usually the maximum
- combines gamete production and mating sucess
what is s
the selection coefficient - or selection differential
3 x origins of adaptive alleles
- new mutation - like melanism in peppered moths or insecticide resistance
- Standing genetic variation - so already there but was neutral or deleterious - repeatability of evolution with sticklebacks
- Adaptive introgression
What is the major consequence of inbreeding
inbreeding depression