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evolution > envs lecture 6 > Flashcards

envs lecture 6 Flashcards

1
Q

what can we predict

A

how much evolution will result from selection acting on a trait / how much evolutionary change is caused by selection acting on a trait

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2
Q

what do evolutionary biologists need to know

A

how much the mean of a given trait will evolve if there’s directional selection

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3
Q

how can we predict how much evolutionary change given by directional selection

A

by calculating the difference between the mean of a trait at start of new generation and mean of the trait now

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4
Q

what is Breeders equation used for

A

to predict the amount of evolutionary change that results from selective breeding

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5
Q

basically what is Breeders equation

A

evolution by directional selection from one generation to the next

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6
Q

what does rate of evolution depend on

A

strength of inheritance and strength of directional selection

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7
Q

what is h^2

A

heritability

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8
Q

what happens if h^2 = 0

A

no resemblance b/w parents and offspring

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9
Q

what happens if h^2 = 1

A

parents and offspring identical

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10
Q

what is the slope of the line equal to

A

heritability

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11
Q

what does Breeders equation show the difference between

A

difference b/w mean trait in next generation and now

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12
Q

what does each point on the graph represent

A

mean of all offspring in single family plotted against mean of their parents

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13
Q

what does no slope mean

A

no relationship b/w mean of parents and mean of offspring in a given trait —> heritability is 0

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14
Q

what does straight/diagonal line slope mean

A

heritability is 1, parents and offspring are identical

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15
Q

equation relating phenotypic, genetic, and environmental variance

A

Vp = Vg + Ve

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16
Q

what is Vp

A

overall phenotypic variance

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17
Q

what is Vg

A

genetic variance (phenotypic variation caused by genetic variation)

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18
Q

what is Ve

A

environmental variance components

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19
Q

what does gene expression depend on

A

age and tissue type, interactions among gene loci, and direct environmental influence

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20
Q

examples of variation in phenotype caused by both genes and environment

A

human height (heritable but influenced by diet)

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21
Q

what is overall phenotypic variation result of

A

combo of genetic variance in a trait and environmental components

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22
Q

what does partitioning genetic variance do? why do we do it?

A

distinguishes role of heredity vs. environment

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23
Q

what is variance of genetic components of Vg

A

Vg = Va + Vd + Vi

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24
Q

what is Va

A

additive genetic variance

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25
Q

what is additive genetic variance

A

the average effect of substituting one allele for another

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26
Q

what is Vd

A

dominane variance

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27
Q

what is dominance variance

A

variance due to dominance of alleles at same locus

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28
Q

does dominance variance contribute to evolutionary change

A

nope, because heterozygotes are not intermediate; they’re gonna exhibit phenotype of dominant allele

29
Q

what is Vi

A

epistatic interactions of alleles at different loci

30
Q

what is epistatic interactions

A

effect of one allele depends on a second allele

31
Q

what contributes to evolutionary change

A

only Va (additive genetic variance)

32
Q

basically what is genetic variance determined by

A

genetic interactions within individuals averaged over the population

33
Q

does Vd cause evolutionary change?

A

no

34
Q

does Vi cause evolutionary change

A

nope

35
Q

do heterozygotes exhibit an intermediate phenotype

A

nope

36
Q

what does the locus exhibit

A

overdominance

37
Q

what is overdominance

A

heterozygous phenotype exhibits a more extreme/different phenotype from either homozygote

38
Q

in this plant example, what happens to the heterozygotes

A

they are taller than either homozygotes

39
Q

what happens if we incorporate selection and all short plants die

A

only heterozygotes are left

40
Q

what happens if only heterozygotes are left

A

frequency of alleles do not change; so no evolutionary change in overdominant locus

41
Q

what is dominance variance

A

heterozygotes are not intermediate w/r to homozygote phenotypes

42
Q

what does additive genetic variation do

A

only variance that contributes to how fast a population evolves in response to directional selection

43
Q

why doesn’t selection cause evolutionary change in this case

A

for most traits, additive genetic variance is larger than dominance variance and epistatic variance

44
Q

what’s up w/ traits with high genetic component (lot of genetic variance)

A

high heritability

45
Q

what does it mean to have a high genetic component

A

a lot of genetic variance

46
Q

examples of traits w/ high genetic component

A

traits like height and length

47
Q

what’s up w/ traits that require lots of resources

A

sensitive to environmental variation

48
Q

describe heritability of traits that are sensitive to environmental variation/require hella resources

A

don’t have as high of heritability

49
Q

examples of traits that require hella resources (not as high heritability)

A

traits like body weight, litter size, age of puberty

50
Q

describe heritability of fecundity and life history characters

A

low heredity

51
Q

why is heritability of fecundity and life history low

A

b/c they are tied to resource availability –> environmental variance

52
Q

what does environmental fluctuation do

A

maintains variation and heritability

53
Q

describe ground finches from Galapagos islands and variation/heritability

A

in drought, food supply is low and seeds are big and hard –> body and bill sizes are large

after el nino –> hella small soft seeds available –> smaller bird w/ smaller bill is favored

54
Q

what does this fluctuating environmental variance lead to

A

variance in selection acting on diff phenotypic traits

55
Q

what is one of the most basic questions we can ask about genetics of quantitative traits

A

what loci contributes to these traits

56
Q

what gene regulates melanic coloration/production of melanin

A

MC1r gene

57
Q

what does MC1r gene produce

A

melanocortin receptor 1 protein

58
Q

what is MCTr gene an example of

A

parallel phenotypic evolution

59
Q

what is parallel phenotypic evolution

A

changes that are parallel at the level of the gene but but at level of nucleotide

60
Q

what does parallel phenotypic evolution lead to

A

changes occur in diff parts of gene in diff organisms, but still same result –> melanization in all of them

61
Q

example of melanic parallel phenotypic evolution

A

AA substitutions in diff parts of protein cause melanization in snow goose, jaguar, mice, etc.

62
Q

what is the genetic basis of this polymorphism (some yellow some melanic) in coloration/melanin

A

few amino acid substitutions in MC1r protein

63
Q

what are other amino acid subs in MC1r important for

A

encoding for red hair in humans and melanism in mice and chickens

64
Q

is MC1r gene also involved in snow geese and arctic skuas light and melanic morphs?

A

yup

65
Q

what is tied to melanin polymorphism in lesser snow goose and parasitic jaeger

A

single amino acid substitutions

66
Q

what is the association b/w particular mutations and

A

degree of melanism

67
Q

what do they mean by particular mutation

A

copy number of variant MC1r alleles

68
Q

what does heterozygotes being intermediate and having multiple copies of gene mean

A

makes the trait quantitative rather than mendelian

69
Q

why do snow geese exhibit wide array of phenotypes rather than just 3

A

Heterozygotes are intermediate and in some cases there may be multiple copies of this gene, which makes the trait become effectively quantitative rather than mendelian

evolution (15 decks)

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