Segregation analysis Flashcards

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1
Q

what is this, mendelial or complex trait if…

  • rare
  • single gene
  • severe mutaion
  • large phenotypic effect
A

Mendelian

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2
Q

what is thi? if the characteristics are

  • common
  • many genes
  • mild mutaitons
  • small phenotypic effect
    *
A
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3
Q

name some susceptibility genes

A
  • BRCA1 (same)
  • BRCA2 (breast, ovarian, prostate cancer)
  • colorectal cancer APC,MYH and others
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4
Q

an example of genes that modify severity?

A

in sickle cell (mild vs severe)

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5
Q

example of modifiers of response to a drug?

A

alternative cytochrome P450 (can increase effect of b-blockers)

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6
Q

what is genetic epidemiology?

A

the study of how and why diseases cluster in families

also answers if disease is due to enviromental exposures or genetics

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7
Q

what is:

  • aggregation studies
  • twin studies and adoption studies
  • segregation analysis
  • linkage studies
  • fine mapping
  • candidate gene studies
A
  • aggregation studies evidence of clustering disease in family?
  • twin studies and adoption studies genetic or enviromenta?
  • segregation analysis is there a GENE? AD? AR?
  • linkage studies where are the genes located?
  • fine mapping & candidate gene studies exact location and polymorphisms
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8
Q

when can you say that there is evidence of familial aggregation?

how do oyu calculate risk?

A
  • when the incidence of disease is higher in the relatives than in controls
  • family hx of disease
  • a higher % cohort with family hx develop disease
  • calculate
    • recurrence risk ration
    • risk of disease in probands/ risk in population
    • risk of disease in relatives of proband / relatives of controls
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9
Q

Risk Ratio Examples

remember the formula

risk of disease in relatives of proband / risk in population

A

cystic fibrosis 0.25 / 0.0004 = 500

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10
Q

who to do twin studies?

A
  • for a mendelian disease
  • with complete penetrance
  • monozygotic
  • dizygotic
  • if MZ have higher concordance than DZ then is genetic effect

ASK the questio when one twin is affected how often is th eother affected?

if MZ=DZ then might be enviroment

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11
Q

what is the purpose of SA segregation analysis?

A
  • study how disease is transmitted
  • determine if AD, AR, x-linked
  • determine is there is evidence of gene effect
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12
Q

what is linkage?

A
  • its statistical method to map genes
  • violation of mendels law
  • its the tendency of 2 or more loci to segregate together in a family
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