lec 15- selection and phenotype evolution

Question 1

what are quantitative traits influenced by?

Answer 1

by multiple additive genes and environmental effects

Question 2

how many alleles affect height?

Answer 2

700 and more

Question 3

how is baby mortality an example of stabilizing selection?

Answer 3

stabilizing selection occurs when individuals with intermediate phenotypes are more likely to survive and reproduce, meaning that babies with normal weight will survive better than extremely high or low weights

Question 4

what is directional selection?

Answer 4

a type of natural selection that shifts a population’s traits in one direction over time, occurs when one extreme phenotype is favored over the other

Question 5

what is disruptive selection?

Answer 5

a type of natural selection that favours extreme traits over normal ones

Question 6

how much a population changes depends on what?

Answer 6

-selection differential (S)
-Heritability: H^2 (broad sense heritability), includes all genetically based variance and h^2 (narrow sense heritability, only includes additive effects of genes

Question 7

when is the phenotypic response the greatest? what is Breeders equation?

Answer 7

when trait is heritable and there is strong selection (S)

R = h^2 x S

Question 8

is phenotypic plasticity common in plants?

Answer 8

yes, leave sizes can be different

Question 9

how does warm water effect the reproductive plasticity of nematodes?

Answer 9

the genetic strains reach maturity progressively faster in warmer environments

Question 10

what mutations in two genes affect melanin production?

Answer 10

mutation 1: in gene MC1R, it decreases sensitivity of signals that would ordinarily produce more dark pigment
mutation 2: in gene Agouti, interferes with signalling of mutation 1, causes reduction in pigment and light fur

both affect mouse fur color

Question 11

do MC1R and Agouti affect fur color in different locations?

Answer 11

yes

Question 12

what gene encodes a receptor protein that triggers pigment production (dark pigment)?

Answer 12

MC1R

Question 13

what gene encodes a repressor protein that shuts down the other genes receptor, producing lighter pigment?

Answer 13

Agouti shuts down MC1R receptor, causing light pigment

Question 14

what are the two hypothesis behind the origin of light coloured mice evolution?

Answer 14

1. all light colored mice evolved form one ancestor based on dark mainland mice
2. light colour evolved more than once, by other gene interactions

Question 15

which light fur mice hypothesis was wrong and right?

Answer 15

-they did not gain the evolution for light fur from one dark ancestor because some mice lack MC1R, rather some gained white fur from allele variations in Agouti gene
-indicating the second hypothesis of it evolving more than once was correct