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BMS2042 > Quantitative Genetics > Flashcards

Quantitative Genetics Flashcards

1
Q

Definition

the rate of probability that two people with shared genes will develop the same organic disease

A

Concordance rate

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2
Q

Define

Multigenic inheritance

A

characteristic that is specified by a combination of multiple genes

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3
Q

Definition

relating to or occurring in a family or its members

A

Familial

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4
Q

A risk figure or recurrent risk can be calculated from what?

A
  • Diagnosis and mode of inheritance
  • Analysis of family pedigree
  • Results of rests - linkage studies etc.
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5
Q

Define

Conditional probability

A

the probability of an event ( A ), given that another ( B ) has already occurred

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6
Q

Define

Discordant

A

showing lack of agreement

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7
Q

If the recurrance risk of autism in siblings = 6%

Incidence of autism in general population = 0.1%

What is the relative risk ratio for siblings?

A

60

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8
Q

Definition

an increased likelihood of developing a particular disease based on a person’s genetic makeup

A

Inherited predisposition

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9
Q

Define

Narrow-sense heritability

A

the degree to which a trait is passed from parent to offspring expressed as the ratio of the additive genetic variance to the total phenotypic variance (VA/VP)

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10
Q

What does dominant genetic variance mean?

A

The animals/plants with the desired trait could be homozygous or heterozygous

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11
Q
A
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12
Q

Define

Index case

A

the first identified case in a group of related cases of a particular communicable or heritable disease

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13
Q

Definition

inheriting the same genetic characteristic

A

Concordant

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14
Q

How can you estimate narrow-sense heritability?

A

Comparing the offspring values against the averaged value for the two parents (mid-parent value)

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15
Q

What are the two common characteristics of quantitative traits?

A
  1. Many genes contribute to one trait = polygenic or multigenic inheritance
  2. The trait can be affected by the environment
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16
Q

What is heritability?

A
  • The proportion of the total phenotypic variation (VP ) in a population that is due to genetic factors
  • Different in different environments
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17
Q

Define

Monozygotic

A

Twins derived from a single ovum, and so identical

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18
Q
A
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19
Q

True or False:

Broad-sense heritability considers GxE interactions

A

False

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20
Q

Define

Empiric risks

A

The chance that a disease will occur in a family, based on experience with the diagnosis, past history, and medical records rather than theory

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21
Q
A
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22
Q

Define

Quantitative trait loci (QTL) mapping

A

a statistical method that links two types of information—phenotypic data (trait measurements) and genotypic data (usually molecular markers)—in an attempt to explain the genetic basis of variation in complex trait

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23
Q

How can you calculate phenotypic variance (VP) from genotypic (VG ), environmental (VE) and genotype-by-environment interaction (VGxE ) variance?

A

VP = VG + VE + VGxE

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24
Q

Definition

when two different genotypes respond to environmental variation in different ways

A

Gene-environment (GxE) interactions

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25
Q

Definition

twins derived from two separate ova, and so not identical

A

Dizygotic

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26
Q

Define

Dizygotic

A

twins derived from two separate ova, and so not identical

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27
Q

Definition

studies conducted on identical or fraternal twins. They aim to reveal the importance of environmental and genetic influences for traits, phenotypes, and disorders

A

Twin studies

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28
Q

Definition

the degree to which a trait is genetically determined expressed as the ratio of the total genetic variance to the phenotypic variance (VG/VP)

A

Broad-sense heritability

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29
Q

Definition

the degree to which a trait is passed from parent to offspring expressed as the ratio of the additive genetic variance to the total phenotypic variance (VA/VP)

A

Narrow-sense heritability

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30
Q

Define

Multifactorial traits

A

traits controlled by multiple genes and the environment

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31
Q

Define

Posterior probability

A

the statistical probability that a hypothesis is true calculated in the light of relevant observations

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32
Q

How many genes would you expect to be involved?

A

Simplify until 1 individual is on each outer end (already done here)

Add up total simplified individuals (64)

64 = 43

So 3 genes are involved

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33
Q

Definition

a probability as assessed before making reference to certain relevant observations, especially subjectively or on the assumption that all possible outcomes be given the same probability

A

Prior probability

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34
Q

Define

Twin studies

A

studies conducted on identical or fraternal twins. They aim to reveal the importance of environmental and genetic influences for traits, phenotypes, and disorders

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35
Q

How do you calculate concordance ratio?

A

MZ concordance / DZ concordance

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36
Q

What type of heritability can be used in animal and plant breeding to determine if a population can be changed by selective breeding?

A

Narrow sense heritability

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37
Q

Define

Concordant

A

inheriting the same genetic characteristic

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38
Q

What methods are used to calculate genetic susceptibility?

A
  1. Population/migration studies
  2. Twin studies
  3. Family studies
  4. Adoption studies
  5. Polymorphism associations - mapping
  6. Biochemical studies
  7. Animal models
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39
Q

Twins are considered concordant when?

A

If they both have the trait in question

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40
Q

Define

Concordance rate

A

the rate of probability that two people with shared genes will develop the same organic disease

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41
Q
A
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42
Q

Define

Inherited predisposition

A

an increased likelihood of developing a particular disease based on a person’s genetic makeup

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43
Q

Definition

a statistical analysis of pedigree data that investigators use to look for evidence of cosegregation of alleles at a genetic “susceptibility” locus and some known genetic “marker” locus (usually a DNA polymorphism) through generations of families

A

Linkage analysis

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44
Q

Definition

events that do not impact the probability of each other occurring

A

Independent events

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45
Q

Define

Genome-wide association studies (GWAS)

A

an observational study of a genome-wide set of genetic variants in different individuals to see if any variant is associated with a trait

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46
Q

What are the 4 steps to Bayesian analysis?

A
  1. Prior probability
  2. Conditional probability
  3. Joint probability
  4. Posterior probability
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47
Q

Definition

a branch of population genetics that deals with phenotypes that vary continuously (in characters such as height or mass)—as opposed to discretely identifiable phenotypes and gene-products (such as eye-colour, or the presence of a particular biochemical)

A

Quantitative genetics

48
Q

How does risk change with number of affected children in single gene vs mutli gene disorder?

A

Single gene: risk remains the same regardless of number affected

Multi gene: risk increases with the number affected

50
Q

What isn’t heritability?

A
  • How much of a trait is genetically determined
  • Ho much of an individual’s phenotype is due to their genotype
  • Fixed for a given trait
51
Q

What is the chance of a child suffering from an autosomal recessive disease if both parents are carriers

52
Q

Define

Bayesian analysis

A

a method of statistical inference in which Bayes’ theorem is used to update the probability for an hypothesis as more evidence or information becomes available

53
Q

Definition

a measure of association between an exposure and an outcome. The OR represents the odds that an outcome will occur given a particular exposure, compared to the odds of the outcome occurring in the absence of that exposure

A

Odds ratio

54
Q

Definition

Twins derived from a single ovum, and so identical

A

Monozygotic

55
Q

What does this graph suggest?

A

G x E interaction is present

56
Q

Definition

A hypothesis to explain quantitative variation by assuming the interaction of a large number of genes (polygenes) each with a small additive effect on the character

A

Multiple gene hypothesis

57
Q

Definition

being related such that each excludes or precludes the other

A

Mutually exclusive

58
Q

Definition

statistical approach that is most commonly used to identify susceptibility loci in complex genetic traits

A

Affected sibling pair (ASP) analysis

59
Q

How do we identify multifactorial disorder genes?

A
  1. Linkage analysis
  2. Affected sibling pair analysis (ASP)
  3. Genome-wide association studies (GWAS)
60
Q

Definition

the likelihood that a hereditary trait or disorder present in one family member will occur again in other family members

A

Recurrence risk

61
Q

Definition

a disease that is not inherited, nor present at birth, but developing after birth

A

Acquired disease

62
Q

Define

Independent events

A

events that do not impact the probability of each other occurring

63
Q

What does Bayes Theorem consider when calculating the overall probability of an event occurring?

A
  1. All initial possibilities (e.g. carrier status)
  2. Additional information (e.g. test results)
64
Q

What does the multiple-gene hypothesis state?

A
  1. A quantitative trait has continuous variation that can be quantified
  2. Two or more genes scattered in the genome account for the hereditary influence on the trait in an additive way
  3. Each gene locus is occupied by either an additive allele or a non-additive allele
  4. The contribution of each additive allele is approximately equal
  5. Together, the additive alleles contributing to a single quantitative character produce substantial phenotypic variation
65
Q

Define

Broad-sense heritability

A

the degree to which a trait is genetically determined expressed as the ratio of the total genetic variance to the phenotypic variance (VG/VP)

66
Q

Define

Prior probability

A

a probability as assessed before making reference to certain relevant observations, especially subjectively or on the assumption that all possible outcomes be given the same probability

67
Q

What does Broad-sense heritability tell us?

A

Tells us the proportion of the variance in a population within a single generation that is due to genetic factors such as dominance and epistasis

68
Q

Twins are considered discordant when?

A

If one has the trait and the other does not

69
Q

Define

Odds ratio

A

a measure of association between an exposure and an outcome. The OR represents the odds that an outcome will occur given a particular exposure, compared to the odds of the outcome occurring in the absence of that exposure

70
Q

Define

Familial clustering

A

the clustering of certain traits, behaviours, or disorders within a given family

71
Q

Definition

the first identified case in a group of related cases of a particular communicable or heritable disease

A

Index case

72
Q

Definition

A physical defect present in a baby at birth that can involve many different parts of the body

A

Congenital malformations

73
Q

Define

Heritability

A

a statistic used in the fields of breeding and genetics that estimates the degree of variation in a phenotypic trait in a population that is due to genetic variation between individuals in that population

74
Q

Definition

the mean value of the product of the deviations of two variates from their respective means

A

Covariance

75
Q

Definition

one of a group of nonallelic genes that together control a quantitative characteristic in an organism

76
Q

How do you calculate relative risk ratio?

77
Q

Define

Multiple gene hypothesis

A

A hypothesis to explain quantitative variation by assuming the interaction of a large number of genes (polygenes) each with a small additive effect on the character

78
Q

Define

Congenital malformations

A

A physical defect present in a baby at birth that can involve many different parts of the body

79
Q

What does each graph portray?

80
Q

In what conditions is it not possible to arrive at a risk figure using Bayesian analysis?

A

Multifactorial disorders

Causal heterogeneity

81
Q

Definition

showing lack of agreement

A

Discordant

82
Q

Definition

the probability of an event ( A ), given that another ( B ) has already occurred

A

Conditional probability

83
Q

Definition

a statistical measure that calculates the likelihood of two events occurring together and at the same point in time

A

Joint probability

84
Q

Definition

the clustering of certain traits, behaviours, or disorders within a given family

A

Familial clustering

85
Q

Definition

a statistical method that links two types of information—phenotypic data (trait measurements) and genotypic data (usually molecular markers)—in an attempt to explain the genetic basis of variation in complex trait

A

Quantitative trait loci (QTL) mapping

86
Q

Definition

the statistical probability that a hypothesis is true calculated in the light of relevant observations

A

Posterior probability

87
Q

Definition

the ratio of the probability of an outcome in an exposed group to the probability of an outcome in an unexposed group

A

Relative risk ratio

88
Q

Definition

a method of statistical inference in which Bayes’ theorem is used to update the probability for an hypothesis as more evidence or information becomes available

A

Bayesian analysis

89
Q

How can you estimate whether a trait is heritable?

A

Look for a correlation between the parents and the offspring

90
Q

Define

Joint probability

A

a statistical measure that calculates the likelihood of two events occurring together and at the same point in time

91
Q

Define

Candidate gene

A

any gene thought likely to cause a disease

92
Q

Define

Relative risk ratio

A

the ratio of the probability of an outcome in an exposed group to the probability of an outcome in an unexposed group

93
Q

Define

Recurrence risk

A

the likelihood that a hereditary trait or disorder present in one family member will occur again in other family members

94
Q

How does affected sibling pair analysis determine candidate genes?

A

If affected siblings inherit a particular chromosome region more or less often than expected by chance, then an allele in that region is involved in some way causing the disease

95
Q

What is the chance of inheriting an autosomal dominant disorder if one parent is a carrier?

96
Q

What does narrow-sense heritability (h2 ) tell us?

A

Tells us the proportion of genetic variation that is due to additive genetic value (VA)

97
Q

Definition

an observational study of a genome-wide set of genetic variants in different individuals to see if any variant is associated with a trait

A

Genome-wide association studies (GWAS)

98
Q

Define

Linkage analysis

A

a statistical analysis of pedigree data that investigators use to look for evidence of cosegregation of alleles at a genetic “susceptibility” locus and some known genetic “marker” locus (usually a DNA polymorphism) through generations of families

99
Q

Definition

any gene thought likely to cause a disease

A

Candidate gene

100
Q

Definition

The chance that a disease will occur in a family, based on experience with the diagnosis, past history, and medical records rather than theory

A

Empiric risks

101
Q

Define

Acquired disease

A

a disease that is not inherited, nor present at birth, but developing after birth

102
Q

How do you calculate joint probability?

A

Prior probability x conditional probability

103
Q

What does fully additive genetic variance mean?

A

That the animals/plants with the desired trait and all homozygotes

104
Q

Define

Polygenic

A

one of a group of nonallelic genes that together control a quantitative characteristic in an organism

105
Q

Define

Gene-environment (GxE) interactions

A

when two different genotypes respond to environmental variation in different ways

106
Q

Using Bayes analysis, determine the probability of II-2 being a carrier

107
Q

Define

Mutually exclusive

A

being related such that each excludes or precludes the other

108
Q

Define

Familial

A

relating to or occurring in a family or its members

109
Q

Definition

characteristic that is specified by a combination of multiple genes

A

Multigenic inheritance

110
Q

Define

Affected sibling pair (ASP) analysis

A

statistical approach that is most commonly used to identify susceptibility loci in complex genetic traits

111
Q

Define

Quantitative genetics

A

a branch of population genetics that deals with phenotypes that vary continuously (in characters such as height or mass)—as opposed to discretely identifiable phenotypes and gene-products (such as eye-colour, or the presence of a particular biochemical)

112
Q

What is the heritability equation (H2)?

A

H2 = VG/VP

Where:

VG = variation due to genotype

VP = proportion of the total phenotypic variation

113
Q

Definition

traits controlled by multiple genes and the environment

A

Multifactorial traits

115
Q

Definition

a statistic used in the fields of breeding and genetics that estimates the degree of variation in a phenotypic trait in a population that is due to genetic variation between individuals in that population

A

Heritability

BMS2042 (9 decks)

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