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GN 311 > Quantitative Genetics > Flashcards

Quantitative Genetics Flashcards

1
Q

What are some qualities of qualitative traits?

A

-discrete phenotypic classes
-discontinuous variation in F2

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2
Q

What are some qualities of quantitative traits?

A

-continuous variation
-no distinct F2 classes

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3
Q

What is the multiple-factor hypothesis?

A

phenotypic expression depends on additive effects, as the number of loci affecting the trait increases so does the number of phenotypic classes

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4
Q

Variation can be due to

A

genotype and the environment

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5
Q

Continuous variation is when

A

the characteristics exhibited cover a continuous range of phenotypes

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6
Q

A “normal distribution” is…

A

a bell-shaped curve.

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7
Q

What are the different components of phenotypic variance?

A

Genotypic Variance, Vg
Environmental Variance, Ve
Additive Genetic Variance, Va
Dominance Genetic Variance, Vd

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8
Q

Phenotypic variance equation

A

Phenotypic variance = Genetic variance (genotype) + environmental variance

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9
Q

Genotypic variance equation

A

Genetic variance=Additive genetic variance + dominance genetic variance

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10
Q

To determine phenotype and genotype equation values you must look at the

A

population

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11
Q

The effect of the gene depends on the…

A

environment in which it is found

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12
Q

Interactions that we will ignore are…

A

Vge is a part of the Vp equation
Vi is a part of the Vg equation

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13
Q

Heritability is used to

A

tell the rate of selection response in a breeding program

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14
Q

Broad-sense heritability is the…

A

phenotypic variance due to some genetic effect

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15
Q

Broad-sense heritability equation

A

H^2=Vg/Vp

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16
Q

Narrow-sense heritability is the…

A

phenotypic variance due to additive genetic effects

17
Q

Narrow-sense heritability equation

A

h^2=Va/Vp
h^2=R/S

18
Q

Heritability ranges from 0 to 1. If it equals 0 then ____________, if it equals 1 then __________.

A

all Vp is due to environmental variation, all Vp is due to genetic variation

19
Q

The higher the heritability the…

A

more progress we can expect from a selection/breeding program

20
Q

Environmental variance equation

A

(Vparent1 + Vparent 2 + Vf1)/3

21
Q

Response to selection is

A

the extent to which the characteristic changes over a generation

22
Q

Selection differential (S) equation

A

S = Xs -Xo
S = (average new breed) - (original average)

23
Q

Response to selection (R) equation

A

R = X1 - Xo
R =(average of offspring) - (average original)

24
Q

Realized heritability equation

A

h^2=R/S

25
Q

Limits to selection response

A

-may decline after selecting a particular characteristic in a population for a long period
-due to genetic variation being lost
-extremes may not be healthy
-two desirable traits may be negatively correlated

26
Q

How are quantitative trait loci mapped using GWAS?

A

They are identified by linkage analysis between the trait and molecular markers. SNPs are used to identify QTL

27
Q

In GWAS anything above the line is

A

statistically different

28
Q

Limitations to heritability

A

-doesn’t say how much genes affect the trait
-individuals don’t have heritability

29
Q

Monozygotic vs Dizygotic Twins

A

-Monozygotic: genetically identical same womb
-Dizygotic: only 50% of genetics shared, different wombs

30
Q

Concordant vs Discordant

A

Concordant: twins same for traits
Discordant: twins differ in trait

31
Q

Twin studies can be used to estimate what?

A

genetic and environmental influences on traits

32
Q

When MZ ratio is high & DZ ratio is low…

A

Indicates significant role of genetic effects

33
Q

Similar MZ & DZ indicates…

A

a lot of variation due to environmental factors

34
Q

When MZ ratio is low & DZ ratio is high…

A

indicates genetic predisposition, but environmental factors are important

GN 311 (5 decks)

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