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Genetics Test III - Jourdan > Lecture 19 > Flashcards

Lecture 19 Flashcards

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1
Q

Heritability

A

The proportion of the total phenotypic variation that is due to genetic difference

-not 100% because environmental factors always play some part

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2
Q

Components of phenotypic variance

Vp=

A

Vg+Ve+Vge

Vg - genetic variance
Ve - environmental variance
Vge - genetic-environ interaction

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3
Q

Components of genetic variance

Vg =

A

Va+Vd+Vi

Va - additive genetic variance
Vd - dominance genetic variance
Vi -genic interaction variance

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4
Q

What are the types of heritability?

A

Broad-sense (H^2 = Vg/Vp; all genetic modifiers)

Narrow-sense (h^2 =Va/Vp; additive effects only)

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5
Q

Heritability by parent-offspring regression

A

h^2 = b or h^2 = 2b

Both parents [b] or 1 parent [2b]

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6
Q

Heritability by elimination of variance components

A

(Vp - Ve = Vg)

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7
Q

Correlation coefficient of mono vs dizygotic twins

A

H^2 = 2(Rmz - Rpz)

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8
Q

If the environmental variance (Ve) increases and all other variance components remain the same, what will the effect be?

a. broad-sense heritability will decrease
b. broad-sense heritability will increase
c. narrow-sense heritability will increase
d. broad-sense heritability will increase, and narrow-sense heritability will increase

A

A

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9
Q

What are the limitations of heritability?

A

Does not indicate the degree to which a characteristic is genetically determined
An individual does not have heritability
There is no universal heritability for a characteristic
Even when high, environmental factors may influence a characteristic
Indicates nothing about the nature of population differences in a characteristic

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10
Q

What can mapping quantitative train locki by linkage analysis accomplish?

A

Help identify genes that help determine differences in quantitative traits

When a marker segregates with a characteristic it means it is closely linked to a locus that influences quantitative trait

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11
Q

Natural selection

A

Selection that arises through the differential reproduction of individuals with different genotypes

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12
Q

Artificial selection

A

Selection by promoting the reproduction of organisms with traits perceived as desirable

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13
Q

Factors influencing response to selection =

A

S

Selection differential

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14
Q

Calculation of response to selection =

A

R
R=h^2 x S

*remember h^2 = narrow sense heritability

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15
Q

Estimating heritability from response to selection =

A

H^2 = R/S; realized heritability

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16
Q

Predicting the response to selection =

A

the extent to which a characteristic subject to selection (interbreeding the extremes) changes in one generation

17
Q

What are limits to selection response?

A

Response may level off after many generations

18
Q

Why does the response to selection often level off after many generations of selection?

A

After many generations, the response to selection plateaus because of two factors

  1. genetic variation may be depleted - all individuals in the population now have the alleles that maximize the quantitative trait; with no genetic variation, there can be no selection or response to selection
  2. even if the genetic variation persists, artificial selection may be limited by an opposing natural selection
19
Q

How is segregation analysis useful?

A

useful in the analysis of non-mendelian or complex genetic disorders that may be polygenic or the result of gene-environment interactions

20
Q

What does segregation analysis estimate?

A

Estimates the approximate mix of genetic and enviromental factors using information from a series of families identified by the researcher

21
Q

What does association analysis examine?

A

Whether affected individuals share the common allele more often than controls

  • random selection of affected and control groups
  • examination of small areas of genome
22
Q

In association analysis, determination of markers is more prevalent in what?

A

Diseased individuals

23
Q

What is the general difficulty with statistical methods?

A

Claims often refuted because of lack of consistency in resutls

24
Q

What are the difficulties in segregation analysis?

A

Choice of families affects results

Multiple genes analyzed together

25
Q

What are the difficulties in association analysis?

A

Small areas of genome examined

Larger areas -> false positives

26
Q

What is regression?

A

A mathematical relationship between correlated variables

27
Q

How is regression used?

A

Used to predict the value of a variable from the value of a correlated variable

28
Q

Broad-sense heritability

A

The portion of phenotypic variance that is due to all types of genetic variance, including additive, dominance, and genic interactions variances

29
Q

Narrow-sense heritability

A

Only that portion of the phenotypic variance that is due to additive genetic variance

30
Q

Heritability is the portion of phenotypic variance due to genetic variance; however, it does not indicate what?

A

What extent the phenotype itself is determined by genotype

31
Q

What does heritability apply to?

A

To populations, not to individuals

32
Q

Heritability is determined for a particular population in a particular environment at a particular time. Heritability determined for ONE population does not apply to what?

A

other populations, or even the same population facing different environmental conditions at different period

33
Q

A trait with high heritability cannot be strongly influenced by environmental factors
True or False?

A

False

It may still be strongly influenced

34
Q

High heritability does not mean that differences between populations are due to differences in genotype
True or False?

A

True

35
Q

How are genes affecting a polygenic characteristic are located with the use of QTL mapping?

A

Two homozygous, highly inbred strains that differ at many loci are crossed and then F1 are interbred.
Quantitative traits are measured and correlated with the inheritance of molecular markers throughout the genome. the correlations are used to infer the presence of a linked QTL

Genetics Test III - Jourdan (6 decks)

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