population genetics 1+2 (mathsy) Flashcards
(11 cards)
what is population genetics
mathematical principles describing how genetic variation changes over space and time. (on a microevolution level)
what is a gene pool
the sum of all the alleles present in a population
what is allele frequency
the proportion of an allele in a gene pool/population
what is the only thing which causes genetic variation
mutations in the dna sequence.
recombination only reshuffles existing variation
what factors impact alle frequency
natural selection
migration into and out of the population (especially effective with rarer alleles)
genetic drift- random fluctuations
what is the hardy weinburg principle
allele frequencies will remain constant across the generations in the absence of other evolutionary factors
what are the conditions that must be met for a population to be in hardy weinburg equilibrium
very large population
random mating/ no sexual selection
no natural selection
isolated population/no migration
no mutations
what are the equations for hardy weinburg and what does each bit mean
p^2 + 2pq + q^2 = 1
p + q = 1
p is the dominant allele frequency
q is the recessive allele frequency
p^2 is the homozygous dominant genotype frequency
2pq is the heterozygous genotype frequency
q^2 is the homozygous recessive genotype frequency
what does the hardy weinberg principle show?
explains how genes are maintained in a population eg. recessive disease are not lost over time as allele frequency is maintained due to carriers (eg. sickle cell disease and malaria)
what kind of genetic diseases are not acted upon by natural selection
late onset such as neurodegenerative disorders. this is because there is no effect on reproductive success.
what is the equation to use when there are multiple alleles eg. blood group
use p,q and r
p2 +2pq +2pr +2qr +q2 =1
p+q+r=1
