lecture 12 Flashcards
what do genetic models of selection allow us to predict
the final outcome of selection = equilibrium allele frequency at a locus
the rate of evolutionary change = the rate of change in the allele frequency at a locus and compare to predicted rate
to examine interaction of selection with other population processes like drift, migration and mutation in so far as the interaction affects allele frequency change
describe natural selection of the dark form of the peppered moth
2 coloured moths
dark form = thick coats of soot from industrial england
white moth disadvantaged = birds will prey on them
genotype aa = white and genotype Aa or AA = dark form
how will natural selection act to alter frequency of allele a (light) in a sooty forest
Particular environment = if change = diff
assume pop originally in hardy weinberg, then natural selection drives AA and Aa frequencies out of HW proportions, mating at random = reestablishes hardy weinberg
how does natural selection typically work
Natural selection typically works by favouring the form with the highest relative fitness
1 = absolute fitness, scale everything to set state (1 = abs), relative decline of 10% so selection coeff = 0.1, relative fitness = easier
describe how natural selection will act to alter the frequency of allele a (parameter q) in a sooty forest environment - suppose that initial freq of q = 0.05
get relative fitness
if in hardy weinberg = have certain frequencies
find Wavg
then freq of genotypes after selection = waafaa /wavg
combo of hardy weinberg and avg population fitness
q drops down as result of natural selection in one gen = white formed a lot = disadvantage in viability
what is the fate of the allele for light pigmentation over many generations….
loss of little a allele
much faster decline bc underestimated fitness values of phenotypes or something else not embodied in model
acts as benchmark
wont rapidly change since recessive allele = rare
by how much will natural selection act to alter frequency of a rare recessive allele (eg q=0.01)
invisible to selection since recessive
most white alleles hidden in heterozygous
q approaches 0 and p approaches 1
loss of variation and pop becomes even more progressively fit = always the case with directional selection
what is balancing selection and describe
like heterozygous advantage for malaria
blood cell sickles enough so malaria wont get it
flower pollination ex = selection that mains variability in population - advantage to being rare, pollinators prefer rare type in pop = visited less than genotype = causes issues
do processes influencing allele frequencies interact
YESSS
not independent of each other
they interac
mutation, migration, selection and genetic drift
focus on interaction between mutation and selection
describe deleterious mutation selection interaction - why bad things happen to good populations
against a deleterious recessive condition = not purged bc mutations w/o getting caught
rate is low
ex = cf
describe deleterious mutation - selection balance
new allele frequency without mutation
new allele frequency assuming mutation = add in effect of mutation - alleles that do not mutate = multiply by 1 and alleles that do mutate multple by 1-u (mutation rate)
p’ = p at eq for completely recessive disease
q’ = sqrt u/s
what is absolute fitness
percent of entire pop that gets to reproductive fitness
