Quantitative Genetics

Question 1

quantitative genetics

Answer 1

the investigation of continuously variable traits that are influenced by the combined effects of many loci as well as environmental factors

Question 2

biometrical school

Answer 2

• initiated by Darwin’s cousin, Galton
• saw heritable variation as continuous
• maintained the idea of slight differences among individuals was the essence of evolution

Question 3

mendelian school

Answer 3

• viewed variation as discrete and sudden, not continuous
• most laboratory geneticists did not believe in evolution by natural selection: too slow & required too subtle variation

Question 4

what to capital letters (B, S) contribute

Answer 4

+1

Question 5

what do lower case letters (b,s) contribute

Answer 5

0

Question 6

many loci =

Answer 6

continuous variation

Question 7

breeding experiment by East

Answer 7

• crossed short & long flowered plants
• produced F1s and F2s
• recovered parental phenotypes by artificial selection

Question 8

logic of breeding experiment by East

Answer 8

if continuous variation is composed of discrete units, the original phenotype should be recoverable

Question 9

variance equation

Answer 9

= sum of (Xi - X0)^2 / n - 1
= omega^2

Question 10

standard deviation =

Answer 10

omega = square root of variance

Question 11

3 kinds of genetic variance

Answer 11

Va + Vd + Vi

Question 12

additive genetic variance, Va

Answer 12

when the phenotypic value for a heterozygote is exactly intermediate between both homozygotes

Question 13

what causes Va?

Answer 13

independent effects of alleles on a phenotype

Question 14

what is additive genetic variance responsible for?

Answer 14

heritable genetic variation

Question 15

dominance variance, Vd

Answer 15

when phenotypic value deviates from additivity

Question 16

what causes dominance variance?

Answer 16

interactions among alleles

Question 17

are dominance effects transmitted directly from parent to offspring? why or why not?

Answer 17

no, because only one allele is contributed by each parent

Question 18

epistatic variance

Answer 18

genetic variation due to interactions among loci

Question 19

is epistatic variance heritable variance? why or why not?

Answer 19

no, because interactions among loci cannot be passed on to offspring due to independent assortment

Question 20

epistasis

Answer 20

the effect of the interaction between two or more loci on the phenotype whereby their joint effects differ from the sum of the loci taken separately

Question 21

is epistasis common?

Answer 21

yes

Question 22

why do you need to know both loci in epistasis?

Answer 22

need to know both loci to predict the influence of an allele on the phenotype

Question 23

environmental variance

Answer 23

differences among individuals in a population that are due to differences in the environments they have experienced

Question 24

the causes of environmental variance, Ve

Answer 24

• environmental effects
• maternal effects
• developmental noise

Question 25

environmental effects as a cause of environmental variance

Answer 25

variation in phenotypic values that is based on environmental factors

Question 26

environmental variation: Clausen, Kreck, & Heisey

Answer 26

- planted cuttings at 3 different elevations in the Sierra Nevada - very different phenotypes

Question 27

what does environmental setting have an impact on?

Answer 27

phenotype

Question 28

maternal effects as a cause of environmental variance

Answer 28

the effect of the mother on phenotypic values for non-genetic reasons

Question 29

example of maternal effects

Answer 29

- egg nutrition levels - egg hormones

Question 30

developmental noise

Answer 30

variance due to random events in development, even under the same condition

Question 31

example of developmental noise

Answer 31

we are not completely symmetrical

Question 32

a phenotypic value is the consequence of the ...

Answer 32

action of your genes within a specific environment

Question 33

what does the variance in phenotypes with in a population often vary with?

Answer 33

the environment

Question 34

what is heritability dependent on?

Answer 34

the environment and the genetic context

Question 35

broad sense heritability

Answer 35

the fraction of phenotypic variation within a population that is due to genetic variation

Question 36

broad sense heritability equation

Answer 36

h^2 = Vg / Vp

Question 37

narrow sense heritability

Answer 37

the fraction of phenotypic variation within a population that is due to additive genetic variation

Question 38

narrow sense heritability equation

Answer 38

h^2 = Va / Vp

Question 39

what is heritability always between

Answer 39

0 - 1

Question 40

is h^2 a symbol or do you square it?

Answer 40

symbol

Question 41

how is narrow sense heritability estimated?

Answer 41

- parent-offspring regression - sib analysis - twin studies - pedigree analysis

Question 42

problems with parent-offspring regression

Answer 42

- misidentified parents - environmental correlation between parents and offspring - maternal effects

Question 43

example of misidentified parents

Answer 43

- nest parasitism - extra pair copulation

Question 44

solution to misidentified parents

Answer 44

genetic testing of paternity

Question 45

solution to environmental correlation between parents and offspring

Answer 45

cross fostering experiments

Question 46

solution to maternal effects

Answer 46

father-offspring regression

Question 47

example of heritability is an environmental-dependent measure

Answer 47

- fruit flies - h^2 = 0.9 for wing width under normal conditions - h^2 = 0.06 under stressful conditions

Question 48

phenotypic plasticity

Answer 48

the capacity for a genotype to express more than one phenotype depending on the environment

Question 49

norm of reaction

Answer 49

the set of phenotypic values of a genotype under different environmental conditions

Question 50

genotype x environmental interaction

Answer 50

difference in the effect of the environment on the phenotype displayed by different genotypes

Question 51

what is the variance of phenotypes in a population dependent on?

Answer 51

interactions between genotypes and the environment

Question 52

can heritability differ between populations? why or why not?

Answer 52

yes, allele frequencies differ between populations even if the environment and everything else is the same

Question 53

does a heritability of 0 mean the trait is not genetically determined?

Answer 53

no