shosh: genetics

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shosh: genetics
2011-07-01 17:36:41

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  1. Codominance
    • Neither allele is dominant
    • Ex: ABO blood groups
  2. Variable expression
    • Severity of phenotype varies from one person to another
    • Ex: neurofibromatosis
  3. Incomplete penetrance
    Not all individuals with a mutant genotype show a mutant phenotype
  4. Pleiotropy
    • One gene has more than one effect on the individual's phenotype
    • Ex: PKU
  5. Imprinting
    • Differences in phenotype depend on whether the mutation is of maternal or paternal origin
    • Ex: Prader-Willi, Angleman's
  6. Anticipation
    • Severity of disease worsens in successive generations
    • Ex: Huntington's
  7. Loss of heterozygosity
    • With a tumor suppressor gene, BOTH alleles must be mutated to turn cancerous
    • Ex: Rb, p53
  8. Dominant negative mutation
    • A heterozygote will produce a mutant protein that prevents the normal protein produced by the non-mutated allele from functioning
    • Ex: mutation of a TF
  9. Linkage disequilibrium
    Tendency for certain alleles at liked loci to occur together
  10. Mosaicism
    • Different cells have different genetic makeup
    • Ex: lyonization
  11. Locus heterogeneity
    • Mutations at different loci produce the same phenotype
    • Ex: Marfan's, MEN 2B and homocysteinuria all produce a marfanoid habitus
  12. Heteroplasmy
    • Presence of normal and mutated mtDNA results in variable expression of a disease
    • Ex: LHON
  13. Uniparental disomy
    Offspring receives two copies of a chromosome from one parent and none from the other parent
  14. Trinucleotide repeat expansion disease
    • Huntington's
    • Friedreich's ataxia
    • Fragile X
    • Myotonic dystrophy