Unit 08: Population Genetics

Question 1

what are SNPs?

Answer 1

differences in nucleotide sequences at a single locus

Question 2

what are microsatellites?

Answer 2

short repeating DNA sequences, the number of repeats differs in each allele

Question 3

which scientist proposed that dominant allele frequencies change over time?

Answer 3

yule

Question 4

which biologists argued that yules assumption of allele frequencies changing over time was wrong?

Answer 4

castle, pearson and punnett

Question 5

what is a gene pool?

Answer 5

the sum of alleles in members of a breeding population at any given time

Question 6

what is the predicted genotypic ratio in HW

Answer 6

1:2:1

Question 7

what is the max frequency of heterozygotes in HW?

Answer 7

50%

Question 8

how do you find the degrees of freedom in a situation where we have a codominant trait?

Answer 8

df = #genotypes - #alleles

Question 9

what is the difference between positive assortative mating and negative assortative mating?

Answer 9

positive - “like with like” mating, increases homozygosity, decreasing genetic variation

negative - decreases homozygosity, maintaining genetic variation in favour of heterozygote

Question 10

what is isolation by distance?

Answer 10

the idea that individuals that are geographically close together tend to mate more

Question 11

what is population structure?

Answer 11

states that if a group of individuals of a certain population mate amongst themselves, the gene pool will be different from another group from the same population mating amongst themselves.

Question 12

what can inbreeding lead to?

Answer 12

inbreeding depression

Question 13

does inbreeding change allelic frequencies?

Answer 13

no just changes genotypic frequency

Question 14

what is inbreeding depression?

Answer 14

the reduced biological fitness due to lack of genetic variation as a result of inbreeding

Question 15

what is the most extreme case of inbreeding?

Answer 15

self-fertilization

Question 16

what is the inbreeding coefficient?

Answer 16

the probability that two alleles in an individual trace back to the same copy in an ancestor

Question 17

what is identical by descent?

Answer 17

when 2 alleles come from a common ancestor

Question 18

what is the formula for the inbreeding coefficient?

Answer 18

(1/2)^n where n = number of transmission events required for IBD

Question 19

what is conservation genetics?

Answer 19

the branch of genetics that looks to design, conduct, and manage captive breeding programs to increase genetics diversity

Question 20

what is the forward mutation rate (miu)?

Answer 20

creation of new A2 alleles by mutating A1

Question 21

what is the reverse mutation rate (v)?

Answer 21

changing A2 alleles to A1 alleles

Question 22

describe the mutation selection balance.

Answer 22

when a recessive trait is selected against but mutation keeps it in the population

Question 23

what are admixed populations?

Answer 23

when new organisms are introduced into a pre-existing population

Question 24

what does it mean when 2 populations are highly diverged?

Answer 24

basically that their N x M is low, so there is little gene flow and they have very different allelic frequencies

Question 25

how much neanderthal and Denisovan DNA do modern genomes contain?

Answer 25

2-4%

Question 26

what is the founder effect?

Answer 26

a v specific case of drift where part of one pop branches off and goes somewhere else changing allelic frequencies

Question 27

what is ellis-van-creveld syndrome a result of?

Answer 27

founder effect when the amish moved to pennsylvania

Question 28

what is a genetic bottle neck?

Answer 28

specific case of drift where some random outside force wipes outa segment of the population

Question 29

what are the conditions for adaptations to occur?

Answer 29

- varying phenotypes - heritable genetic variation - more offspring born than will survive (struggle for existence) - some genetic variants produce more offspring than others

Question 30

what is darwinian fitness?

Answer 30

the ability to survive AND reproduce

Question 31

what defines absolute fitness?

Answer 31

the number off offspring has as more offspring = more alleles contributed in population

Question 32

is there random mating involved in absolute fitness?

Answer 32

nope!

Question 33

what is relative fitness?

Answer 33

quantification of the reproductive success of a genotype compared to the most successful genotype in the population

Question 34

what is the difference between positive and purifying seletion?

Answer 34

positive - increasing frequency of favoured allele purifying - decreasing frequency of unfavoured allele

Question 35

what is directional natural selection?

Answer 35

natural selection where phenotypes in the population are shifted towards a homozygote

Question 36

if you increase a dominant allele by a certain mount of units, how much will the recessive allele decrease?

Answer 36

the same amount

Question 37

what are the allelic frequencies of a fixed allele?

Answer 37

p = 1 and q = 0

Question 38

why cant an allele every actually be fixed tho?

Answer 38

mutations and migration can shift allelic frequencies

Question 39

what is balance polymorphism?

Answer 39

when alleles reach an equilibrium, maintaining the heterozygote but pushing against the recessive homozygote

Question 40

describe heterozygote advantage when it comes to hemoglobin and malaria.

Answer 40

recessive variants cause sickle cell anemia which is BAD but the heterozygote condition gives resistance to malaria so survivability of heterozygotes is larger than dom. homozygotes