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Genetics > Chapter 28 - Complex and Quantitative Traits > Flashcards

Chapter 28 - Complex and Quantitative Traits Flashcards

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1
Q

These are characteristics that are determined by several genes are significantly influenced by environmental factors

A

Complex traits

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2
Q

Most complex traits are these - traits that can be described numerically

A

Quantitative traits

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3
Q

This is the study of the mode of inheritance of complex and quantitative traits

A

Quantitative genetics

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4
Q

What are four types of quantitative traits?

A

Anatomical, physiological, behavioral, disease

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5
Q

Some quantitative traits are these - can be expressed in whole numbers

A

Meristic traits

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6
Q

Diseases are often this type of quantitative trait - traits that are inherited due to the contributions of many genes

A

Threshold traits

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7
Q

Do quantitative traits naturally fall into a small number of discrete categories?

A

No

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8
Q

This is an alternative way to describe quantitative traits

A

Frequency distribution

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9
Q

How is a frequency distribution for a quantitative trait constructed?

A

Trait is divided arbitrarily into a number of discrete phenotypic categories

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10
Q

Frequency distributions for quantitative trait often form this type of distribution

A

Normal distribution

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11
Q

These two scientists showed that many traits in animals are quantitative

A

Francis Galton and Karl Pearson

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12
Q

Francis Galton and his student Karl Pearson founded this field of genetics to study quantitative traits in animals

A

Biometric field of genetics

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13
Q

Genetics is often interested in the amount of this that exists in a group

A

Phenotypic variation

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14
Q

A common way to evaluate variation within a population is with a statistic called this

A

Variance

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15
Q

Why are variances very important in the analysis of quantitative traits?

A

They are additive under certain conditions

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16
Q

The variances of genetic and environmental factors that contribute to a quantitative trait can be added to predict this

A

Total variation for that trait

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17
Q

Taking the square root of the variance is a statistic called this

A

Standard deviation

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18
Q

If the values in a population follow a normal distribution, then it is easier to appreciate the amount of variation by considering this

A

Standard deviation

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19
Q

In many biological problems it is useful to compare these

A

Two different variables

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20
Q

This describes the degree of variation between two variables within a group

A

Covariance

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21
Q

To calculate this statistic, the covariance needs to be determined first

A

Correlation coefficient

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22
Q

Correlation coefficient evaluates this

A

Strength of association between two variables

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23
Q

What is the range of values for the correlation coefficient?

A

+1 to -1

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24
Q

What does a correlation coefficient of > 0 indicate?

A

As one factor increases, the other factor will increase with it

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25
Q

What does a correlation coefficient of 0 indicate?

A

The two factors are not related

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26
Q

What does a correlation coefficient of < 0 indicate?

A

As one factor increases, the other factor will decrease

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27
Q

What is the null hypothesis for testing correlation?

A

There is no real correlation

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28
Q

Like the chi square value, the significance of the correlation coefficient is directly related to these two factors

A

Sample size and degrees of freedom

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29
Q

What are two assumptions that must be met to make correlation testing valid?

A
  1. The values of X and Y are obtained by an unbiased sampling of the entire population; 2. The scores of X and Y follow a normal distribution and that the relationship between X and Y is linear
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30
Q

Most quantitative traits are this, meaning they are influenced by two or more genes and exhibit a continuum of phenotypic variation

A

Polygenic

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31
Q

This refers to the transmission of traits that are governed by two or more genes

A

Polygenic inheritance

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32
Q

This Swedish scientist studied polygenic inheritance in oats and wheat

A

H. Nilsson-Ehle

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33
Q

Many polygenic traits are especially difficult or impossible to categorize into several discrete genotypic categories when these two things are true

A
  1. The number of genes controlling the trait increases (3 or more); 2. The influence of the environment increases
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34
Q

Can a Punnett square be used to analyze most quantitative traits?

A

No

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35
Q

This is the location on a chromosome that harbors one or more genes that affect the outcome of a quantitative trait

A

Quantitative trait locus (QTL)

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36
Q

This is the basis for quantitative trait locus (QTL) mapping

A

Association between genetically determined phenotypes for quantitative traits and molecular markers

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37
Q

These are used as reference points along chromosomes and can be RFLPs or microsatellites

A

Molecular markers

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38
Q

The general strategy for QTL mapping involves this

A

Two different, highly inbred strains of a diploid species

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39
Q

In QTL mapping, the inbred strains of a diploid species must be different in these two important ways

A
  1. Differ in quantitative trait of interest (i.e., large vs small fruit); 2. Differ in many molecular markers
40
Q

Can a geneticist ever actually determine the relative amount of a quantitative trait that is controlled by genetics vs the environment?

A

No

41
Q

Instead of determining how much genetics vs the environment control a quantitative trait, geneticists focus on how this will affect the phenotypic results

A

Variation

42
Q

To study quantitative trait variation, both of these variances must be considered

A

Genetic variance (V_G) and Environmental variance (V_E)

43
Q

Variance due to interactions between genetic environmental factors is expressed as this

A

V_GxE

44
Q

Variance due to associations between genetic and environmental factors is expressed as this

A

V_G<->E

45
Q

V_GxE expresses variance due to these between genetic and environmental factors

A

Interactions

46
Q

V_G<->E expresses variance due to these between genetic and environmental factors

A

Associations

47
Q

What is the expression for phenotypic variance?

A

V_P = V_G + V_E

48
Q

In the expression for phenotypic variance, what does V_P stand for?

A

Total phenotypic variance

49
Q

In the expression for phenotypic variance, what does V_G stand for?

A

Relative amount of variance due to genetic variation

50
Q

In the expression for phenotypic variance, what does V_E stand for?

A

Relative amount of variance due to environmental factors

51
Q

To study phenotypic variance, these two assumptions may be made

A
  1. Genetic and environmental factors are the only two components that determine a trait; 2. These factors are independent of one another
52
Q

This is when genetics and environment interact

A

Genotype-environment interaction

53
Q

This is when certain genotypes are preferentially found in a particular environment

A

Genotype-environment association

54
Q

Is genotype-environment association very common in human genetics?

A

Yes

55
Q

What are two ways to correct for genotype-environment association when studying human genetics?

A
  1. Looking at identical vs fraternal twins; 2. Looking at siblings adopted by different families
56
Q

This is the amount of phenotypic variation within a group of individuals that is due to genetic variation

A

Heritability

57
Q

If all the phenotypic variation in a group was due to genetic variation, heritability would have a value of this

A

1

58
Q

If all the phenotypic variation in a group was due to environmental factors, heritability would have a value of this

A

0

59
Q

What are the two types of heritability?

A

Broad sense and narrow sense

60
Q

This type of heritability takes into account different types of genetic variation that may affect the phenotype

A

Broad sense heritability

61
Q

Geneticists usually subdivide V_G into these three different genetic categories

A
  1. Variance due to additive effects of alleles (V_A); 2. Variance due to alleles that follow a dominant/recessive pattern of inheritance (V_D); Variance due to the effects of alleles that interact in an epistatic manner (V_I)
62
Q

This type of heritability only takes into account the additive effects of alleles

A

Narrow sense heritability

63
Q

Which category of genetic variance do geneticists usually focus on in analyzing quantitative traits?

A

V_A (variance due to alleles)

64
Q

What are the three steps in estimating narrow sense heritability?

A
  1. Measure a quantitative trait among groups of genetically related individuals; 2. Use data to compute correlation between individuals; 3. Calculate narrow sense heritability as β„Ž_𝑁^2 = π‘Ÿ_obs/π‘Ÿ_exp
65
Q

What is the expression for calculating narrow sense heritability?

A

β„Ž_𝑁^2 = π‘Ÿ_obs /π‘Ÿ_exp

66
Q

What does r_obs represent in the calculation for narrow sense heritability?

A

Observed phenotypic correlation between related individuals

67
Q

What does r_exp represent in the calculation for narrow sense heritability?

A

Expected correlation based on known genetic relationship

68
Q

For siblings that aren’t identical twins, what does r_exp equal?

A

0.5

69
Q

For identical twins, what does r_exp equal?

A

1.0

70
Q

For parent-offspring relationships, what does r_exp equal?

A

0.5

71
Q

For an uncle-niece relationship, what would r_exp equal?

A

0.25

72
Q

This scientist was the first to study human fingerprint patterns

A

Francis Galton

73
Q

This scientist made human fingerprint patterns more amenable to genetic studies

A

Kristine Bonnevie

74
Q

Kristine Bonnevie developed a method for counting these within a human fingerprint

A

Dermal ridges

75
Q

What are the three categories of human fingerprint patterns?

A

Arch, loop, whorl

76
Q

What is the primary difference between different fingerprint patterns?

A

Presence/number of triple junctions

77
Q

Triple junctions in human fingerprints are also known as this

A

Triradius

78
Q

This type of fingerprint pattern has no triradius

A

Arch

79
Q

This type of fingerprint pattern has 1 triradius

A

Loop

80
Q

This type of fingerprint pattern has 2 triradii

A

Whorl

81
Q

This is the modification of phenotypes in plant and animal species of economic importance by human intervention

A

Selective breeding

82
Q

This is another term for selective breeding

A

Artificial selection

83
Q

This type of selection is due to natural variation in reproductive success

A

Natural selection

84
Q

This is a consequence of inbreeding in which genetic variation within a group is reduced and homozygosity for deleterious alleles is increased

A

Inbreeding depression

85
Q

Quantitative traits are often at this value in unselected populations

A

Intermediate

86
Q

This is the point at which selective breeding will have no additional effect, as the population is monomorphic for all or most of the desirable alleles

A

Selection limit

87
Q

Response to selection is a common way to estimate this heritability

A

Narrow sense heritability

88
Q

This is the response to selection estimated by narrow sense heritability

A

Realized heritability

89
Q

What is the expression for calculating realized heritability?

A

β„Ž_𝑁^2 = 𝑅/𝑆

90
Q

What does R stand for in the calculation for realized heritability?

A

Response in the offspring to selection (difference between mean of offspring and mean of starting population)

91
Q

What does S stand for in the calculation for realized heritability?

A

Selection differential in parents (difference between mean of parents and mean of starting population)

92
Q

This is when two different inbred strains are crossed to each other and the offspring are more vigorous than either parent

A

Heterosis (or hybrid vigor)

93
Q

What are the two major hypotheses to explain heterosis?

A

Dominance hypothesis and overdominance hypothesis

94
Q

This scientist proposed the dominance hypothesis in 1908 to explain the genetic basis for heterosis

A

Charles Davenport

95
Q

These two scientists proposed the overdominance hypothesis in 1908 to explain the genetic basis for heterosis

A

George Shull and Edward East

Genetics (11 decks)

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