Population genetics

Question 1

hardy weinberg model

Answer 1

2 alleles in diploid individual are randomly and independently sampled from an infinitely large pool of gametes
p(A)=p
p(a)=q

Question 2

assumptions of hardy weinberg

Answer 2

large population
random mating
no migration
no mutation
no selection
all so that nothing is changing allele frequencies

Question 3

no mutation

Answer 3

no new alleles

Question 4

random mating

Answer 4

no assortative, inbreeding or outbreeding

Question 5

no migration

Answer 5

allele frequencies not influences by variation in other populations

Question 6

infinitely large population

Answer 6

no sampling error=constant allele frequencies=mathematically simple model

Question 7

no selection

Answer 7

alleles dont affect fitness
no alleles selected for

Question 8

prediction 2

Answer 8

after one generation of random mating, genotype frequencies will align to p^2+2pq+q^2

Question 9

prediction 1

Answer 9

allele frequencies of a population dont change solely due to random mating

Question 10

where are rare alleles mainly found

Answer 10

heterozygotes

Question 11

when is the frequency of heterozygotes greatest

Answer 11

when p=q=0.5

Question 12

when the frequency of one allele is high, most individuals are…

Answer 12

homozygotes

Question 13

allele frequencies calculation

Answer 13

a diploid population of N individuals will have 2N alleles
f(A)=(2nAA+nAa) / 2N

Question 14

genotypic frequencies calculation

Answer 14

f(AA)=number of AA individuals / N

Question 15

non random mating

Answer 15

can affect genotype frequencies but not allele frequencies unless accompanied by other evolutionary forces
some combinations of alleles will occur at a higher frequency than expected

Question 16

positive assortative mating

Answer 16

genetically/phenotypically similar individuals tend to mate with each other

Question 17

negative assortative mating

Answer 17

genetically or phenotypically dissimilar
individuals tend to mate with each other
promotes heterozygosity

Question 18

inbreeding

Answer 18

individuals tend to mate with relatives
increases homozygosity and reduces heterozygosity

Question 19

assortative mating

Answer 19

Phenotype-biased mating means frequencies of certain genotypes, in loci underlying the phenotype, will be altered
Affects heterozygosity
This effect is not genome-wide, though it can be multiple loci

Question 20

measuring inbreeding

Answer 20

considering whether an individual has a pair of alleles that are identical by descent

Question 21

identical by state alleles

Answer 21

by random chance, individuals can have a pair of alleles that are the same but not because they are from a recent ancestor

Question 22

inbreeding coefficient, F

Answer 22

probability that two alleles sampled at a locus are identical by descent
inbred has to be homozygote for trait

Question 23

genotypic frequencies equations for inbreeding

Answer 23

f(AA)=p^2+pqF
f(Aa)=2pq-2pqF
f(aa)=q^2+pqF
where F is the proportional reduction in the frequency of heterozygotes compared to that expected in the hardy weinberg model

Question 24

inbreeding depression

Answer 24

when inbreeding results in reduced viability and fecundity (fitness)
Must be caused by a general pattern of lower fitness of homozygotes compared to heterozygotes

Question 25

cause of inbreeding depression

Answer 25

Inbreeding increases homozygosity across the genome. Leads to homozygosity at some loci harbouring deleterious recessive alleles
many generations of inbreeding can allow natural selection to purge such alleles

Question 26

genetic load

Answer 26

represents the reduction in a population’s average fitness due to the presence of deleterious alleles. Even though deleterious alleles may reduce fitness when homozygous, they persist because they are often “hidden” in heterozygous individuals where selection cannot effectively remove them.

Question 27

mutation-selection balance

Answer 27

This is the equilibrium between:
Mutation, which introduces new deleterious alleles into the population.
Selection, which removes these alleles when they appear in homozygous individuals.
The balance ensures that deleterious alleles are not completely eliminated but remain at low frequencies in the population.

Question 28

why do allele frequencies change

Answer 28

genetic drift
natural selection
migration

Question 29

genetic drift

Answer 29

random changes in allele frequencies
smaller populations more affected

Question 30

for any allele frequency, the expected amount of ‘error’ is proportional to

Answer 30

1/2N
where 2N is the total number of alleles

Question 31

bottlenecks

Answer 31

huge reduction in population size
can cause drift events

Question 32

founder effect

Answer 32

allele frequencies very different from original population
reduces heterozygosity

Question 33

fitness

Answer 33

the average contribution to the next generation made by an individual or genotype

Question 34

overdominance

Answer 34

heterozygous genotype has a higher fitness than either of the homozygous genotypes
neither allele is favoured/selected for
selection maintains both alleles in the population

Question 35

migration

Answer 35

Isolated populations will tend to become more different from each other in allele frequencies over time (differences in local pattern of selection, differences caused by drift)
Migration opposes this process and reduces genetic differences between populations, through exchange

Question 36

factors increasing genetic variation within populations (summary)

Answer 36

mutation
migration
some types of natural selection

Question 37

factors increasing genetic variation between populations (summary)

Answer 37

mutation
genetic drift
some types of natural selection

Question 38

factors decreasing genetic variation within populations (summary)

Answer 38

genetic drift
some types of natural selection

Question 39

factors decreasing genetic variation between populations (summary)

Answer 39

migration
some types of natural selection