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BIO342 > Genetic and Phenotypic Variation II > Flashcards

Genetic and Phenotypic Variation II Flashcards

1
Q

Define quantitative genetic variation.

A

Variation among individuals in a phenotypic trait that is due to genetic differences at multiple Mendelian inherited loci.

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2
Q

How does quantitative genetic variation cause said variation to appear continuous?

A

The influence of multiple genes on a trait causes the variation to appear as continuous.

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3
Q

What is another term for quantitative genetic variation?

A

Polygenetic traits

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4
Q

Define each variable in this equation.

A

V means variance
Here we calculate total variance by summing:
Variance due to genotype, variance due to environment and variance due to error

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5
Q

What is genetic variance (Vg)?

A

The absolute variance in a trait due to genetic differences among individuals.

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6
Q

What is heritability?

A

The proportion of the total phenotypic variation in the population due to genetic differences among individuals.

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7
Q

What is the quantitative range for heritability values?

A

Heritability varies between 0 (no heritability) to 1 (complete heritability).

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8
Q

How is heritability calculated?

A

Vg/VTotal

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9
Q

What are the two main methods used to quantify heritability?

A

Parent-offspring regression
Family or sib-design

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10
Q

How does parent-offspring regression work?

A
  • Estimates heritability by comparing trait similarity between parents and offspring
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11
Q

Outline the procedure for parent-offspring regression.

A
  1. Plot mean offspring value against mid-parental value
  2. Calculate the line of best fit using ordinary least-squares (OLS) regression (linear regression)
  3. The slope of this line = heritability
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12
Q

What are the two main benefits of parent-offspring regression?

A

o Allows you to directly study traits inherited between generations
o Allows estimation of heritability within natural populations

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13
Q

What are the two main limitations of parent-offspring regression?

A

o Assumes parents’ environment is the same as offsprings’ environment
o Changes in environment between generations can alter phenotypes

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14
Q

How does sib-design work?

A
  • Estimates heritability by comparing traits among clones or siblings
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15
Q

Outline the procedure for sib-design.

A
  1. Grow/rear replicate offspring individuals from multiple clones or families
  2. Randomize a common environment
  3. Estimate variance among families/genotypes, environmental variance and error variance
  4. Calculate heritability = Vgenotype/Vtotal
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16
Q

What are the benefits of sib-design experiments?

A

o Common gardens allow heritability to be estimated without confounding effects of environment
o Flexible breeding designs

17
Q

What are the two limitations of sib-designs?

A

o Not all species are willing to be reared in a common garden
o Obtaining adequate replication can be problematic

18
Q

This was the general equation for determining total variance. However, Vgenotype can actually be broken into 4 subtypes of variance. What are they?

A

VAdditive
VDominance
VEpistasis
VMaternal/epigenetic

19
Q

What is dominant genetic variance?

A

Variance due to dominant effects of alleles

20
Q

What is epistatic genetic variance?

A

Variance due to interactions between alleles at different loci

21
Q

What is maternal variance?

A

maternally inherited genetic (i.e., mitochondria, plastids) and environmental (provisioning) differences leading to variance.

22
Q

What is epigenetic variance?

A

phenotypic variation due to epigenetic modifications

23
Q

What is additive genetic variance?

A

most accurately predicts the response to selection

24
Q

What are estimates of heritability based on additive genetic variance called?

A

Narrow-sense heritability

25
Q

What are estimates of heritability based on genetic variance called?

A

Broad-sense heritability

26
Q

What is this equation for? Define all variables.

A

Broad-sense heritability (H^2) equation
VG = genetic variance
VT = total variance

27
Q

What is this equation for? Define all variables.

A

Narrow-sense heritability (h^2)
Va = additive genetic variance
VT = total variance

28
Q
A

BIO342 (21 decks)

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