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Genomics > Genetics of Disease Susceptibility > Flashcards

Genetics of Disease Susceptibility Flashcards

1
Q

What are the components of a complex disease?

A
  1. Environment
  2. Epigenetic & regulatory events
  3. Genome allelic variants
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2
Q

The role of genetics in complex diseases is largely relegated to what?

A

Collection of family medical history (shared genetics + environment; raw estimate of overall risk)

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3
Q

The missing heritability problem is the variants discovered by GWAS only explain a (major/minor) fraction of expected heritability

A

minor

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4
Q

The missing heritability problem is the variants discovered by GWAS only explain a minor fraction of expected heritability. This may be because of the effect sizes….

A

are much smaller than previously thought

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5
Q

The missing heritability problem is the variants discovered by GWAS only explain a minor fraction of expected heritability. We may have (over/under) estimated the heritability

A

over

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6
Q

The missing heritability problem is the variants discovered by GWAS only explain a minor fraction of expected heritability. It is (common/rare) variants that contribute most of the variation

A

Rare

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7
Q

The missing heritability problem is the variants discovered by GWAS only explain a minor fraction of expected heritability. What accounts for much of the resemblance among relatives?

A

Epigenetic inheritance

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8
Q

The missing heritability problem is the variants discovered by GWAS only explain a minor fraction of expected heritability. Do the genotyping chips tag casual variants?

A

They do, but not very effective though

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9
Q

What is heritability?

A

Proportion of variance of phenotype in a POPULATION that can be attributed to genotypic differences

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10
Q

Example of discrete phenotype

A

Disease status

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11
Q

Example of categorical phenotype

A

Number of digits

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12
Q

Example of continuous phenotype

A

Height or biochemical measure

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13
Q

How can you estimate heritability using studies?

A

Use twin studies

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14
Q

Is heritability a statement about individuals?

A

Nope

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15
Q

Is heritability a statement about a single population?

A

Yurp

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16
Q

Is heritability the same as inheritance?

A

Nope

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17
Q

What is the Common Disease / Common Variant (CDCV) model?

A

Most disease susceptibility can be attributed to 10 to 20 specific loci (explains around 5% disease risk)

18
Q

What is the subset model of CDCV?

A

Infinitesimal loci model

19
Q

What is the infinitesimal loci model?

A

We carry thousands of weak susceptibility alleles

Those who are unlucky have too many and are at highest risk

Those who have rare variants or environmental triggers push us over the edge which implies a threshold

20
Q

What is the Rare alleles of Major Effect (RAME) model?

A

Diseases are highly heterogenous with lots of rare mutations causing individual cases of disease

21
Q

What are some cases for the CDCV model?

A
  1. Infinitesimal model is well validated in quantitative genetics
  2. Common variants capture most of genetic variance in GWAS
22
Q

What are some cases against the CDCV model?

A

The missing heritability has not been account for in many common diseases

23
Q

What are some cases for the RAME model?

A
  1. Evolutionary theory predicts that disease alleles should be rare
  2. Many rare familial disorders are due to rare alleles of large effect
24
Q

What are some cases against the RAME model?

A
  1. Sibling recurrence rates are greater than postulated effect sizes of rare variants
  2. Epidemiological transitions cannot be attributed to rare variants
25
Q

What is epigenetics?

A
  1. Histone modifications

2. Study of heritable changes that do not affect DNA sequence

26
Q

(+/-) charged DNA is wrapped on (+/-) charged histones

A

Negative - DNA

Positive - Histones

27
Q

What are the ways histones are chemically altered by?

A
  1. Acetylation

2. Methylation

28
Q

Which histone change allows increased expression of DNA?

A

Acetylation

29
Q

Histone acetylation allows what to DNA?

A

Increase expression (as a result of decreasing charge of histones + attraction to DNA)

30
Q

Which histone change allows decreased expression of DNA?

A

Methylation

31
Q

Histone methylation allows what to DNA?

A

Decrease expression (As a result of tightening of DNA coil + histones)

32
Q

Can methylation patterns be inherited?

A

Yes

33
Q

(T/F) Methylation of specific genes is heritable and impacts which copy of genes are expressed

A

True

34
Q

(T/F) Acetylation of specific genes is heritable and impacts which copy of genes are expressed

A

False

35
Q

Imprinting (promotes/prevents) complementation

A

prevents

36
Q

Any mutation (as a result of imprinting) in the expressed gene will result in (phenotype/genotype)

A

phenotype

37
Q

What is allelic heterogeneity?

A

Different mutations in the SAME gene

38
Q

What is locus heterogeneity?

A

Mutations in several DIFFERENT genes

39
Q

What is a modifier gene?

A

Genes that influence expression of other genes aka epistasis

40
Q

What is pleiotropy?

A

One gene causes multiple phenotypes

41
Q

What is penetrance/expressivity?

A

Varying proportion of phenotype observed given a particular geneotype

Genomics (11 decks)

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