cycle 6

Question 1

population genetics

Answer 1

involve many individuals, no controlled crosses, don’t show Mendelian ratios

Question 2

no selection in a population

Answer 2

frequency of all genotypes stay constant, allele frequencies also stay the same

Question 3

selection against the dominant phenotype

Answer 3

frequency of genotypes that include dominant allele go to 0, recessive goes to 100

Question 4

what happens when allele frequencies change?

Answer 4

evolution occurs

Question 5

microevolution

Answer 5

change in allele frequencies that occurs from one generation to the next within a population

Question 6

macroevolution

Answer 6

speciation, the evolution of a new species

Question 7

hardy-weinberg principle

Answer 7

if a population experiences no selection, mutation, immigration/emigration, genetic drift, and is randomly mating then it is in HWE

Question 8

HWE allele vs genotype frequencies

Answer 8

observed allele frequencies:
-dominant (p), recessive (q)
expected genotype frequencies:
-homozygous dominant (p^2), heterozygous (2pq), homozygous recessive (q^2)

P + Q = 1

Question 9

how to tell if a population is in HWE by frequencies?

Answer 9

a population is in HWE if expected genotype frequencies match observed genotype frequencies

Question 10

why determine if a population is in HWE?

Answer 10

used to predict genotype frequencies, helps to indicate if a population might be evolving or if individuals are not mating randomly

Question 11

absolute fitness (W)

Answer 11

a measurable quantity, sometimes a proxy for # of offspring

Question 12

relative fitness (w)

Answer 12

absolute fitness divided by the absolute fitness of the most successful genotype (w=W/Wmax)
-most successful genotype has w=1

Question 13

selection against the dominant phenotype relative fitness

Answer 13

WBB = WBR < WRR

Question 14

selection against the recessive phenotype relative fitness

Answer 14

WBB = WBR > WRR

Question 15

heterozygote advantage relative fitness

Answer 15

WBB < WBR > WRR

Question 16

heterozygote disadvantage relative fitness

Answer 16

WWW > WWS < WSS

Question 17

allele frequencies in selection against the dominant phenotype

Answer 17

frequency of dominant allele goes to 0, frequency of recessive allele goes to 100% (fixation)

Question 18

allele frequencies in selection against the recessive phenotype

Answer 18

frequency of the recessive allele never goes to 0 (because of heterozygotes)

• because selection acts on phenotypes not genotypes
• impossible to eliminate recessive alleles

Question 19

heterozygote advantage and malaria

Answer 19

heterozygous for disease, mild anaemia but also resistance to malaria

Question 20

heterozygote advantage

Answer 20

maintains genetic variation, balancing selection, rare alleles increase in frequency and common alleles decrease (for 2 allele system, each allele will reach 0.5 frequency)

Question 21

heterozygote disadvantage

Answer 21

results in less genetic variation, common alleles have the advantage and rare alleles decrease in frequency (can disappear)

Question 22

heterozygote advantage and disadvantage

Answer 22

occurs if heterozygotes have a different phenotype than homozygotes (incomplete dominance/codominance)

Question 23

directional selection

Answer 23

one of the extremes are favoured

Question 24

stabilizing selection

Answer 24

mean is favoured

Question 25

disruptive selection

Answer 25

both extremes are favoured

Question 26

balancing selection

Answer 26

each phenotype is favoured

Question 27

gene flow

Answer 27

any movement of individuals (or genetic material) from one population to another (alleles added/lost from populations)

Question 28

genetic drift

Answer 28

by chance (not everyone will reproduce), change in allele frequencies due to the effect of chance, anyone can mate with anyone and pass one any one of their alleles; e.g. survival during a severe storm- randomly lost alleles, but rare alleles are more likely to be completely lost

Question 29

bottleneck and founder effect

Answer 29

change in allele frequencies due to random sampling of a very small number of individuals; catastrophic reduction in population (bottleneck) or small number of founders (founder)
-leads to reduced genetic variation

Question 30

consequences of genetic drift

Answer 30

reduces genetic variation, beneficial mutations are rare and have a higher probability of being lost, can lead to an increased frequency of often recessive deleterious alleles (especially in bottleneck/founder)

Question 31

consequences of bottleneck and founder effects

Answer 31

small populations lead to inbreeding (increased homozygosity), increase in phenotypes of recessive deleterious traits

Question 32

non-random mating

Answer 32

individuals select mates based on phenotype, does not cause changes in allele frequencies (assortative mating, inbreeding, disassortative mating, inbreeding avoidance)
-leads to a departure from HWE, but not evolution because allele frequencies stay the same

Question 33

assortative mating

Answer 33

leads to an increased frequency of homozygotes- assortative mating among relatives leads to inbreeding (homozygosity across the genome)

Question 34

consequences of inbreeding

Answer 34

increase in homozygosity exposes phenotype of deleterious recessive alleles, increases the prevalence of these harmful phenotypes (inbreeding depression- low lifespan)

Question 35

disassortative mating

Answer 35

leads to increased heterozygosity- mating between unrelated individuals is inbreeding avoidance
-can lead to heterozygote advantage in organisms