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How do we study the effect of genes on disease risk?
• DNA has many ‘variants’: places where the coding between individuals in a population differs
DNA Variation
Polymorphisms (common, >1:1000) Mutations (rare, <1:1000)
Types:
• Single Nucleotide Polymorphisms
(SNPs)
• Variable Number Tandem Repeats (VNTRs), e.g. mini/microsatellite markers
• Structural variation: insertions/deletions/duplications
Genetic Variation
heritable vs. somatic
Germ-line (heritable) Somatic
Origin: transmission from parents (+ de novo at conception)
Typically present in every cell (Exception: ‘mosaicism’)
Constitutes ‘heritability’ of traits and diseases
Origin: mutation event in DNA of a single cell
Present in selected cells; in tissues through clonal expansion
Basis for most cancers
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