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Principals of Evolution > Quantitative Genetics > Flashcards

Quantitative Genetics Flashcards

1
Q

quantitative genetics

A

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

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2
Q

biometrical school

A
  • initiated by Darwin’s cousin, Galton
  • saw heritable variation as continuous
  • maintained the idea of slight differences among individuals was the essence of evolution
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3
Q

mendelian school

A
  • 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
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4
Q

what to capital letters (B, S) contribute

A

+1

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5
Q

what do lower case letters (b,s) contribute

A

0

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6
Q

many loci =

A

continuous variation

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7
Q

breeding experiment by East

A
  • crossed short & long flowered plants
  • produced F1s and F2s
  • recovered parental phenotypes by artificial selection
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8
Q

logic of breeding experiment by East

A

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

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9
Q

variance equation

A

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

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10
Q

standard deviation =

A

omega = square root of variance

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11
Q

3 kinds of genetic variance

A

Va + Vd + Vi

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12
Q

additive genetic variance, Va

A

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

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13
Q

what causes Va?

A

independent effects of alleles on a phenotype

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14
Q

what is additive genetic variance responsible for?

A

heritable genetic variation

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15
Q

dominance variance, Vd

A

when phenotypic value deviates from additivity

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16
Q

what causes dominance variance?

A

interactions among alleles

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17
Q

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

A

no, because only one allele is contributed by each parent

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18
Q

epistatic variance

A

genetic variation due to interactions among loci

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19
Q

is epistatic variance heritable variance? why or why not?

A

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

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20
Q

epistasis

A

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

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21
Q

is epistasis common?

A

yes

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22
Q

why do you need to know both loci in epistasis?

A

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

23
Q

environmental variance

A

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

24
Q

the causes of environmental variance, Ve

A
  • environmental effects
  • maternal effects
  • developmental noise
25
Q

environmental effects as a cause of environmental variance

A

variation in phenotypic values that is based on environmental factors

26
Q

environmental variation: Clausen, Kreck, & Heisey

A
  • planted cuttings at 3 different elevations in the Sierra Nevada
  • very different phenotypes
27
Q

what does environmental setting have an impact on?

A

phenotype

28
Q

maternal effects as a cause of environmental variance

A

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

29
Q

example of maternal effects

A
  • egg nutrition levels
  • egg hormones
30
Q

developmental noise

A

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

31
Q

example of developmental noise

A

we are not completely symmetrical

32
Q

a phenotypic value is the consequence of the …

A

action of your genes within a specific environment

33
Q

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

A

the environment

34
Q

what is heritability dependent on?

A

the environment and the genetic context

35
Q

broad sense heritability

A

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

36
Q

broad sense heritability equation

A

h^2 = Vg / Vp

37
Q

narrow sense heritability

A

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

38
Q

narrow sense heritability equation

A

h^2 = Va / Vp

39
Q

what is heritability always between

A

0 - 1

40
Q

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

A

symbol

41
Q

how is narrow sense heritability estimated?

A
  • parent-offspring regression
  • sib analysis
  • twin studies
  • pedigree analysis
42
Q

problems with parent-offspring regression

A
  • misidentified parents
  • environmental correlation between parents and offspring
  • maternal effects
43
Q

example of misidentified parents

A
  • nest parasitism
  • extra pair copulation
44
Q

solution to misidentified parents

A

genetic testing of paternity

45
Q

solution to environmental correlation between parents and offspring

A

cross fostering experiments

46
Q

solution to maternal effects

A

father-offspring regression

47
Q

example of heritability is an environmental-dependent measure

A
  • fruit flies
  • h^2 = 0.9 for wing width under normal conditions
  • h^2 = 0.06 under stressful conditions
48
Q

phenotypic plasticity

A

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

49
Q

norm of reaction

A

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

50
Q

genotype x environmental interaction

A

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

51
Q

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

A

interactions between genotypes and the environment

52
Q

can heritability differ between populations? why or why not?

A

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

53
Q

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

A

no

Principals of Evolution (18 decks)

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