Topic 8: Population Genetics

Question 1

________ genetics can be traced back to the early 1900’s

Answer 1

population genetics

Question 2

_______________________________: occurs in a population where there is random mating, no natural selection, no mutation, no migration, no genetic drift (i.e. PERFECT conditions)

Answer 2

Hardy-Weinberg Equilibrium

Question 3

_________ frequencies are stable at p + q = 1 for two alleles

Answer 3

allelic frequencies

Question 4

________ frequencies are distributed according to p^2 + 2pq + q^2 = 1

Answer 4

genotypic frequencies

Question 5

_____ is a group of interbreeding organisms

Answer 5

population

Question 6

________ is the collection of genes and alleles in a population, distributed to genotypes

Answer 6

gene pool

Question 7

what are the two methods to determining H-W equilibrium?

Answer 7

genotype proportion/frequency method

allele-counting method

Question 8

how do we use the genotype proportion/frequency method? what are the two main equations?

Answer 8

f(A) = p^2 + pq
f(B) = q^2 + pq

Question 9

what is the equation used for genotypes when dealing with three alleles?

Answer 9

p^2 + 2pr + r^2 + 2rq + q^2 + 2pq = 1

Question 10

what is the main example used when dealing with three alleles and the H-W equilibrium?

Answer 10

blood types, A/B/O

Question 11

true/false: for sex-linked traits, genotypic frequencies will differ between males and females under H-W equilibrium

Answer 11

true! Depending on if its X or Y linked (in humans at least!)

Question 12

when assuming H-W equilibrium and attempting a Chi-Square test, what are our H0 and Ha

Answer 12

H0: pop. is in H-W equilibrium
Ha: pop. is NOT in H-W equilibrium

Question 13

what are the degrees of freedom for a H-W chi-square analysis?

Answer 13

DF= (# genotypes) - (# alleles)

Question 14

who came up with natural selection?

Answer 14

Charles Darwin

Question 15

true/false: natural selection doesn’t change H-W equilibrium in populations

Answer 15

false!! it will change allelic frequencies

Question 16

________ reproductive fitness “favours the most fit”

Answer 16

differential reproductive fitness

Question 17

___________ quantifies the reproductive success of a genotype compared to the most favored genotype in a population

Answer 17

relative fitness (w)

Question 18

true/false: genotypes with the greatest relative fitness have a w=1

Answer 18

true!

Question 19

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

Answer 19

selection coefficient

Question 20

_________ selection shifts the phenotypes in the population to the homozygous genotype

Answer 20

directional natural selection

Question 21

true/false: eventually, directional selection can “fix” an allele

Answer 21

true! it never truly gets fixed though, because there are so many other factors that shift allelic freq.

Question 22

_________: alleles reach an equilibrium, selective pressure favours maintaining heterozygotes but selects against homozygous recessive

Answer 22

balance polymorphism

Question 23

____________: develop when the fitness of heterozygotes is higher than the fitness of both homozygotes in a given population

Answer 23

heterozygote advantage (main example: hemoglobin and sickle-cell disease!!)

Question 24

true/false: mutations change frequencies

Answer 24

true!

Question 25

_______ mutation rate: creates new A2 alleles by mutating A1

Answer 25

forward mutation rate (mu)

Question 26

_______: changes A2 alleles by mutation to A1

Answer 26

reverse mutation rate (v)

Question 27

true/false: forward and reverse mutation rates ca create a balanced equilibrium in the absence of other factors

Answer 27

true

Question 28

true/false: mutations are often subject to natural selection

Answer 28

true

Question 29

_________-__________ balance: natural selection removes the recessive trait, but mutation keeps it in the population

Answer 29

mutation-selection balance

Question 30

________/migration moves alleles into and out of populations

Answer 30

gene flow

Question 31

_________ populations: additions of new organisms into an existing population

Answer 31

admixed

Question 32

_________ model: one-way flow of genes/individuals

Answer 32

island-model residents = 1-m (m=migrants)

Question 33

________ increases genetic variation and decreases divergence (by adding a bunch of new people!)

Answer 33

gene flow

Question 34

______: causes allele frequency change by sampling error

Answer 34

genetic drift (because not all alleles in a small sample are sampled in the same frequencies as the large pop.)

Question 35

true/false: genetic drift is more noticeable in smaller populations but does occur in all populations

Answer 35

true

Question 36

true/false: allele frequency changes due to drift aren't random

Answer 36

false

Question 37

in absence of all evolutionary forces, genetic drift will cause alleles to become ______ in a population and eliminate all other alleles

Answer 37

fixed (flat on graph- no change!)

Question 38

______ effect: a new, small population branches off a larger one

Answer 38

founder effect

Question 39

true/false: founders of the new pop. are a random draw from the larger pop.

Answer 39

true! totally random (ex: Ellis-van Crevald syndrome in a very specific Amish community)

Question 40

____________ occurs when a large population is drastically reduced to a small population

Answer 40

bottleneck effect (due to catastrophes, natural disasters- survivors have low genetic diversity due to HUGE loss of alleles from gene pool)

Question 41

true/false: bottleneck effect can effect a single population or an entire species

Answer 41

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!)

Question 42

______ is a form of non-random mating

Answer 42

inbreeding

Question 43

does inbreeding change the genotypic frequencies in a population?

Answer 43

yes! doesn;t change allelic frequencies, but redistributes genotypic frequencies because we see an increase in homozygosity compared to heterozygosity

Question 44

Sewell Wright studied inbreeding and produced the _______________ (F)

Answer 44

coefficient of inbreeding (F)

Question 45

coefficient of inbreeding (F): the probability that two alleles carried in an individual are homozygous... _________

Answer 45

identical by descent (IBD)

Question 46

true/false: inbreeding results in a higher occurrence of exact same alleles through generations

Answer 46

true! and we can track individual alleles through pedigrees

Question 47

____________ depression increases the homozygosity within a population, which in small populations can reduce the overall fitness if the population/species

Answer 47

inbreeding depression

Question 48

___________ looks to design, conduct, and manage captive inbreeding programs to increase genetic diversity

Answer 48

conservation genetics

Question 49

assortative mating is another form of ______ mating

Answer 49

nonrandom mating, only affects genes associated with mate choice

Question 50

1. mutations _____ genetic variation 2. selection _____/_____ genetic variation and population divergence 3. inbreeding _____ homozygotes 4. assortative mating ______/______ homozygotes 5. drift ______ genetic variation, _____ population divergence 6. migration ______ genetic variation, ______ pop. divergence

Answer 50

1. increases 2. increases/decreases 3. increases 4. increases/decreases 5. increase, decrease 6. increase, decrease