LEC47: Population Genetics Flashcards
population genetics is?
the application of genetic principles to entire populations or organisms
population = group of organisms of same species living in same geographical area
subpopulation?
may be within a population
allele frequencies can vary across subpopulations
what marks evolution of a population over time
changes in allele (genotype) frequency
allele frequncy?
proportion of **chromosomes **in a population carrying a particular allele at some locus
genotype frequency?
proportion of **individuals **in a population w/ a particular genotype at some locus
what does Hardy-Weinberg equilibrium state?
in a large population, allele frequency for autosomal traits will achieve and remain in a state of equilibirum after 1 generation of random mating
if you know the frequency of the allele in the population, you can estimate the frequence of the genotype in the population
what are population conditions for H-W equilibirum to work?
holds in a model population that’s
1) infinitely large or large enough to neglect errors,
2) mating occurs randomly,
3) there’s no advantage for any genotype,
4) no migration,
5) no new mutations
what is the formula of the H-W equilibrium? name the varibles
p = allele A
q = allele a
p2 = homozygous genotype AA
q2 = homogous genotype aa
2pq = htereozygous genotype Aa
p+q = 1
p2 + 2pq + q2 = 1
what does H-W say about allele frequencies?
allelic frequencies will remain constant over time if certain conditions are met:
random mating
absence of distributing forces like migration, mutation, and selection in a given gene
what can cause deviation from H-W equilibrium expected frequencies?
1) genotyping errors
2) selection
3) genetic drift
4) non-random mating
5) population structure
why does natural selection occur? what does it cause?
drives evolution of adaptive traits
occurs as result of fact that more organisms can survive and reproduce
thus selection, propagation, reproduction of genotypes that confer enhanced ability to survive and reproduce
if an allele confers ability to survive, it is reproduced over time
does natural selection work w/ H-W equilibrium
no
are humans exempt from natural selection?
no
think - 30% of pregnancies end by spontaneous abortion of embryos & fetuses, = **mortality selection **
& of those who marry, ~10% won’t have children, = fecundity selection
what is genetic drift?
in each generation, some individuals may by chance leave behind a few more descendents (& genes) than others
genes of next generation will be genes of those “lucky” individuals, not the healthier/”better” individuals
happens to all populations
is an entirely random process, unlike natural selection
does not produce adaptations
what are founder effects
genetic drift means population can have high frequency of a gene that causes disease, if its present in that population and there isnt mixing