Unit 09: Quantitative Genetics

Question 1

qualitative traits have ____ categories

Answer 1

discrete

Question 2

qualitative traits display a ____ phenotypic range

Answer 2

discontinuous

Question 3

quantitative traits display ___ variation

Answer 3

continuous

Question 4

what are meristic traits? give an example.

Answer 4

quantitative traits that have discrete values.

ex. clutch size in nesting birds (cant lay half an egg)

Question 5

what are major genes?

Answer 5

genes that in polygenic traits contribute the most to the trait compared to other genes

Question 6

what are the major genes involved in eye colour?

Answer 6

OCA2 and HERC2

Question 7

what is the function of OCA2 in determining eye colour?

Answer 7

determine how much melanin is present. higher expression = darker iris

Question 8

what is the function of HERC2 in determining eye colour?

Answer 8

regulates expression of OCA2

Question 9

what are modifier genes?

Answer 9

genes in a polygenic trait that contribute a small effect to the phenotype

Question 10

what is the formula for individuals who exhibit a phenotypic extreme?

Answer 10

1/2^n where n = # alleles

Question 11

what are additive genes?

Answer 11

genes that cause a continuous phenotypic range because of incremental contributions from multiple genes

Question 12

who proposed the multi gene hypothesis?

Answer 12

hermann nilsson-ehle

Question 13

what is the multi gene hypothesis?

Answer 13

the idea that segregation of alleles from multiple genes contributes to phenotypic variation

Question 14

the more phenotypic classes we have, the less _____ they are from each other

Answer 14

discernable

Question 15

what is the formula to find number of phenotypes due to additive alleles?

Answer 15

2n + 1 where n = number of genes

Question 16

what happen when there is no genotypic x environmental interaction?

Answer 16

discontinuous f1 genotypic ratio of 1:2:1

Question 17

what happen when there is lots of genotypic x environmental interaction?

Answer 17

continuous f1 with much phenotypic overlap

Question 18

what is Vg in inbred populations?

Answer 18

0

Question 19

what is the formula for Vp?

Answer 19

Vg + Ve

Question 20

what is an example of positive correlation?

Answer 20

taller people have larger feet

Question 21

what are familial traits? give an example

Answer 21

traits shared by family for any reasons.

ex. scandinavians all typically have blonde hair, blue eyes and light skin

Question 22

what are heritable traits? give an example

Answer 22

similar traits in family members due to genes.

ex. bone structure

Question 23

what is heritability?

Answer 23

the proportion of phenotypic variation that is due to genetic factors

Question 24

what does high heritability mean?

Answer 24

most phenotypic variation is due to genetic factors

Question 25

which traits are most impacted by natural selection?

Answer 25

traits with high heritability

Question 26

what is broad sense heritability?

Answer 26

estimates the proportion of phenotypic variation due to total genotypic variation

Question 27

what is the formula for broad sense heritability?

Answer 27

H^2 = Vg/Vp

Question 28

what is narrow sense heritability?

Answer 28

estimates the proportion of phenotypic variation due to additive genotypic variation

Question 29

what is the formula for narrow sense heritability?

Answer 29

h^2 = Va/Vp

Question 30

heritability is accurate only for:

Answer 30

the environment which the population exists and is measured in

Question 31

can traits with high heritability be affected by the environment?

Answer 31

yes

Question 32

what is the formula for Vg?

Answer 32

Va + Vd + Vi

Question 33

who used broad sense heritability to describe the genetic contribution to eye tissue in cave fish?

Answer 33

horst wilkens

Question 34

what did horst wilkens find in the dark cave stream fish?

Answer 34

reduced eye tissue

Question 35

studies in phenotypic traits of human _____ can provide insight into broad sense heritability

Answer 35

twins

Question 36

what is the formula to determine Vp in monozygotic (identical) twins?

Answer 36

Vp = Ve

Question 37

what is the formula to determine Vp in dizygotic (fraternal) twins?

Answer 37

Vp = Ve + 1/2(Vg)

Question 38

why can heritability studies in twins be prone to error?

Answer 38

- stronger shared maternal effects in identical twins - greater similarity of treatment in identical twins than fraternal - greater similarity in interaction between genes and environment in identical twins than fraternal

Question 39

what is concordance?

Answer 39

the % of twin pairs where both have the same phenotypic expression of a trait

Question 40

what is discordance?

Answer 40

the % of twin pairs where both have different phenotypes for a trait

Question 41

if phenotypic variation is 100% genetic, monozygotic twins should always be _____ for the trait

Answer 41

concordant

Question 42

if phenotypic variation is 100% genetic, dizygotic twins should always be _____ for the trait

Answer 42

50% concordant

Question 43

what occurs in regards to concordance if phenotypic variation for a trait is not solely genetic?

Answer 43

DZ and MZ twins will have approx equal concordance in their traits

Question 44

in a narrow sense heritability plot, what value is the heritability?

Answer 44

the slope

Question 45

what is the selection differential?

Answer 45

difference between population mean value for a trait and mean value for a trait in the mating portion of the population

Question 46

what is the formula for the selection differential?

Answer 46

s = mean mating - mean pop

Question 47

what is the selection response?

Answer 47

difference between the mean in the offspring for a trait and the mating population

Question 48

what is the formula for the selection differential?

Answer 48

R = S(h^2) OR R = mean offspring - mean original pop

Question 49

genetic correlations always showcase a ____ of sorts

Answer 49

compromise

Question 50

describe directional selection.

Answer 50

mean phenotypic value is shifted to either extreme , narrowing the phenotypic range and changing the mean and reducing variance

Question 51

describe stabilizing selection.

Answer 51

selection favours an intermediate phenotype without changing the mean and reducing variance.

Question 52

describe disruptive selection.

Answer 52

selection favours both extreme phenotypes without changing the mean and increasing variance.