Lecture 8 Flashcards
(24 cards)
When is natural selection more powerful, and why?
more powerful in large populations, as drift is weaker
What can happen to a beneficial allele as population size gets smaller?
as population size gets smaller, sometimes you may actually lose your beneficial allele. Due to dirft and chance events
What happens to selection when you have strong drift?
when you have strong drift, have weaker selection since drift overpowers it
In what population would a beneficial allele go to fixation the fastest
A large population as we wouldn’t have factors such as drift messing things up
What is directional selection?
one genotype has higher itness than the other
What is heterozygote disadvantage?
our heterozygote has lower fitness than the alternate homozygotes
What is heterozygote advantage?
When there is a benefit to being a heterozygote compared to the homozygotes
What is directional selection?
directional selection means that one of the two alleles has higher fitness than the other one
What does the response to selection depend on?
depends on the pairing of the allele (dominant, recessive, heterozygote, homozygote)
What does the rate of the allele frequency depend on?
depends on the selection coefficient and dominance
What is the selection coefficient (s)?
fitness disadvantage to genotype
What is dominance coefficient (h)?
proportion of s applied to the heterozygote genotype (how much selective disadvantage to the heterozygote)
What frequency do we give our beneficial genotype?
a fitness of one
where is heterozygote disadvantage found?
not found in nature, impossible
What is negative frequency dependent selection?
an allele becomes less fit as it becomes more common
What occurs in a stable polymorphism?
multiple alleles will be maintained in a stable polymorphism (both alleles are maintained), promotes genetic diveristy
When would negative frequency dependent selection occur?
pathogen, mating, resource use, predation
What is positive frequency dependent selection?
an allele becomes more fit as it becomes more common
What does positive frequency dependence lead to?
leads to unstable polymorphism (maintainng both alleles is unstable), wants to go to one genotype or the other
Does directional selection remove or maintain variation?
removes
Does heterozygotous advantage maintain or remove variation?
maintains
Does heterozygous disadvtange remove or maintain variation?
removes
Does negative frequency dependent model maintain or remove variation?
maintain
Does positive frequency dependent model remove or maintain variation?
removes
