envs lecture 6

Question 1

what can we predict

Answer 1

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

Question 2

what do evolutionary biologists need to know

Answer 2

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

Question 3

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

Answer 3

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

Question 4

what is Breeders equation used for

Answer 4

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

Question 5

basically what is Breeders equation

Answer 5

evolution by directional selection from one generation to the next

Question 6

what does rate of evolution depend on

Answer 6

strength of inheritance and strength of directional selection

Question 7

what is h^2

Answer 7

heritability

Question 8

what happens if h^2 = 0

Answer 8

no resemblance b/w parents and offspring

Question 9

what happens if h^2 = 1

Answer 9

parents and offspring identical

Question 10

what is the slope of the line equal to

Answer 10

heritability

Question 11

what does Breeders equation show the difference between

Answer 11

difference b/w mean trait in next generation and now

Question 12

what does each point on the graph represent

Answer 12

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

Question 13

what does no slope mean

Answer 13

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

Question 14

what does straight/diagonal line slope mean

Answer 14

heritability is 1, parents and offspring are identical

Question 15

equation relating phenotypic, genetic, and environmental variance

Answer 15

Vp = Vg + Ve

Question 16

what is Vp

Answer 16

overall phenotypic variance

Question 17

what is Vg

Answer 17

genetic variance (phenotypic variation caused by genetic variation)

Question 18

what is Ve

Answer 18

environmental variance components

Question 19

what does gene expression depend on

Answer 19

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

Question 20

examples of variation in phenotype caused by both genes and environment

Answer 20

human height (heritable but influenced by diet)

Question 21

what is overall phenotypic variation result of

Answer 21

combo of genetic variance in a trait and environmental components

Question 22

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

Answer 22

distinguishes role of heredity vs. environment

Question 23

what is variance of genetic components of Vg

Answer 23

Vg = Va + Vd + Vi

Question 24

what is Va

Answer 24

additive genetic variance

Question 25

what is additive genetic variance

Answer 25

the average effect of substituting one allele for another

Question 26

what is Vd

Answer 26

dominane variance

Question 27

what is dominance variance

Answer 27

variance due to dominance of alleles at same locus

Question 28

does dominance variance contribute to evolutionary change

Answer 28

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

Question 29

what is Vi

Answer 29

epistatic interactions of alleles at different loci

Question 30

what is epistatic interactions

Answer 30

effect of one allele depends on a second allele

Question 31

what contributes to evolutionary change

Answer 31

only Va (additive genetic variance)

Question 32

basically what is genetic variance determined by

Answer 32

genetic interactions within individuals averaged over the population

Question 33

does Vd cause evolutionary change?

Answer 33

no

Question 34

does Vi cause evolutionary change

Answer 34

nope

Question 35

do heterozygotes exhibit an intermediate phenotype

Answer 35

nope

Question 36

what does the locus exhibit

Answer 36

overdominance

Question 37

what is overdominance

Answer 37

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

Question 38

in this plant example, what happens to the heterozygotes

Answer 38

they are taller than either homozygotes

Question 39

what happens if we incorporate selection and all short plants die

Answer 39

only heterozygotes are left

Question 40

what happens if only heterozygotes are left

Answer 40

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

Question 41

what is dominance variance

Answer 41

heterozygotes are not intermediate w/r to homozygote phenotypes

Question 42

what does additive genetic variation do

Answer 42

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

Question 43

why doesn't selection cause evolutionary change in this case

Answer 43

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

Question 44

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

Answer 44

high heritability

Question 45

what does it mean to have a high genetic component

Answer 45

a lot of genetic variance

Question 46

examples of traits w/ high genetic component

Answer 46

traits like height and length

Question 47

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

Answer 47

sensitive to environmental variation

Question 48

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

Answer 48

don't have as high of heritability

Question 49

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

Answer 49

traits like body weight, litter size, age of puberty

Question 50

describe heritability of fecundity and life history characters

Answer 50

low heredity

Question 51

why is heritability of fecundity and life history low

Answer 51

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

Question 52

what does environmental fluctuation do

Answer 52

maintains variation and heritability

Question 53

describe ground finches from Galapagos islands and variation/heritability

Answer 53

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

Question 54

what does this fluctuating environmental variance lead to

Answer 54

variance in selection acting on diff phenotypic traits

Question 55

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

Answer 55

what loci contributes to these traits

Question 56

what gene regulates melanic coloration/production of melanin

Answer 56

MC1r gene

Question 57

what does MC1r gene produce

Answer 57

melanocortin receptor 1 protein

Question 58

what is MCTr gene an example of

Answer 58

parallel phenotypic evolution

Question 59

what is parallel phenotypic evolution

Answer 59

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

Question 60

what does parallel phenotypic evolution lead to

Answer 60

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

Question 61

example of melanic parallel phenotypic evolution

Answer 61

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

Question 62

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

Answer 62

few amino acid substitutions in MC1r protein

Question 63

what are other amino acid subs in MC1r important for

Answer 63

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

Question 64

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

Answer 64

yup

Question 65

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

Answer 65

single amino acid substitutions

Question 66

what is the association b/w particular mutations and

Answer 66

degree of melanism

Question 67

what do they mean by particular mutation

Answer 67

copy number of variant MC1r alleles

Question 68

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

Answer 68

makes the trait quantitative rather than mendelian

Question 69

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

Answer 69

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