Topic 8: Population Genetics Flashcards
________ genetics can be traced back to the early 1900’s
population genetics
_______________________________: occurs in a population where there is random mating, no natural selection, no mutation, no migration, no genetic drift (i.e. PERFECT conditions)
Hardy-Weinberg Equilibrium
_________ frequencies are stable at p + q = 1 for two alleles
allelic frequencies
________ frequencies are distributed according to p^2 + 2pq + q^2 = 1
genotypic frequencies
_____ is a group of interbreeding organisms
population
________ is the collection of genes and alleles in a population, distributed to genotypes
gene pool
what are the two methods to determining H-W equilibrium?
genotype proportion/frequency method
allele-counting method
how do we use the genotype proportion/frequency method? what are the two main equations?
f(A) = p^2 + pq
f(B) = q^2 + pq
what is the equation used for genotypes when dealing with three alleles?
p^2 + 2pr + r^2 + 2rq + q^2 + 2pq = 1
what is the main example used when dealing with three alleles and the H-W equilibrium?
blood types, A/B/O
true/false: for sex-linked traits, genotypic frequencies will differ between males and females under H-W equilibrium
true! Depending on if its X or Y linked (in humans at least!)
when assuming H-W equilibrium and attempting a Chi-Square test, what are our H0 and Ha
H0: pop. is in H-W equilibrium
Ha: pop. is NOT in H-W equilibrium
what are the degrees of freedom for a H-W chi-square analysis?
DF= (# genotypes) - (# alleles)
who came up with natural selection?
Charles Darwin
true/false: natural selection doesn’t change H-W equilibrium in populations
false!! it will change allelic frequencies
________ reproductive fitness “favours the most fit”
differential reproductive fitness
___________ quantifies the reproductive success of a genotype compared to the most favored genotype in a population
relative fitness (w)
true/false: genotypes with the greatest relative fitness have a w=1
true!
The _____________ is a measure of the extent to which natural selection is acting to reduce the relative contribution of a given genotype to the next generation
selection coefficient
_________ selection shifts the phenotypes in the population to the homozygous genotype
directional natural selection
true/false: eventually, directional selection can “fix” an allele
true! it never truly gets fixed though, because there are so many other factors that shift allelic freq.
_________: alleles reach an equilibrium, selective pressure favours maintaining heterozygotes but selects against homozygous recessive
balance polymorphism
____________: develop when the fitness of heterozygotes is higher than the fitness of both homozygotes in a given population
heterozygote advantage (main example: hemoglobin and sickle-cell disease!!)
true/false: mutations change frequencies
true!
_______ mutation rate: creates new A2 alleles by mutating A1
forward mutation rate (mu)
_______: changes A2 alleles by mutation to A1
reverse mutation rate (v)
true/false: forward and reverse mutation rates ca create a balanced equilibrium in the absence of other factors
true
true/false: mutations are often subject to natural selection
true
_________-__________ balance: natural selection removes the recessive trait, but mutation keeps it in the population
mutation-selection balance
________/migration moves alleles into and out of populations
gene flow
_________ populations: additions of new organisms into an existing population
admixed
_________ model: one-way flow of genes/individuals
island-model
residents = 1-m (m=migrants)
________ increases genetic variation and decreases divergence (by adding a bunch of new people!)
gene flow
______: causes allele frequency change by sampling error
genetic drift (because not all alleles in a small sample are sampled in the same frequencies as the large pop.)
true/false: genetic drift is more noticeable in smaller populations but does occur in all populations
true
true/false: allele frequency changes due to drift aren’t random
false
in absence of all evolutionary forces, genetic drift will cause alleles to become ______ in a population and eliminate all other alleles
fixed (flat on graph- no change!)
______ effect: a new, small population branches off a larger one
founder effect
true/false: founders of the new pop. are a random draw from the larger pop.
true! totally random (ex: Ellis-van Crevald syndrome in a very specific Amish community)
____________ occurs when a large population is drastically reduced to a small population
bottleneck effect (due to catastrophes, natural disasters- survivors have low genetic diversity due to HUGE loss of alleles from gene pool)
true/false: bottleneck effect can effect a single population or an entire species
true! (northern elephant seals were allowed to re-populate after being hunted down, now the new and large population has next to no genetic diversity- they have fixed alleles!)
______ is a form of non-random mating
inbreeding
does inbreeding change the genotypic frequencies in a population?
yes! doesn;t change allelic frequencies, but redistributes genotypic frequencies because we see an increase in homozygosity compared to heterozygosity
Sewell Wright studied inbreeding and produced the _______________ (F)
coefficient of inbreeding (F)
coefficient of inbreeding (F): the probability that two alleles carried in an individual are homozygous… _________
identical by descent (IBD)
true/false: inbreeding results in a higher occurrence of exact same alleles through generations
true! and we can track individual alleles through pedigrees
____________ depression increases the homozygosity within a population, which in small populations can reduce the overall fitness if the population/species
inbreeding depression
___________ looks to design, conduct, and manage captive inbreeding programs to increase genetic diversity
conservation genetics
assortative mating is another form of ______ mating
nonrandom mating, only affects genes associated with mate choice
- mutations _____ genetic variation
- selection _____/_____ genetic variation and population divergence
- inbreeding _____ homozygotes
- assortative mating ______/______ homozygotes
- drift ______ genetic variation, _____ population divergence
- migration ______ genetic variation, ______ pop. divergence
- increases
- increases/decreases
- increases
- increases/decreases
- increase, decrease
- increase, decrease
