Updated: 1/5/2017

Biochemical Model Systems

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Model systems
  • Transgenic mice
    • construction
      • germline modification
        • cloned gene (transgene) introduced into a fertilized mouse ovum
        • constitutive
          • non-specific insertion into genome
        • conditional
          • specific (targeted) insertion into genome
      • the altered phenotype with the added gene is observed through the entire lifespan
        • including embryonic development
      • number of gene copies is variable
      • altered phenotype passed to offspring as it is a germline mutation
    • function
      • studying dominant disorders
        • due to the fact that the transgene will coexist with normal gene product
  • Knockout mice
    • construction
      • similar to transgenic mice except instead of adding a foreign gene, a normal gene is removed
      • also a germline modification
    • function
      • useful for studying loss-of-function mutations in human diseases
  • Chimeric mice
    • construction
      • a genetic mix between two distinct cell lines
      • fusion of two early embryogenic lines in embryogenesis
      • two lines recognized as self due to absence of immune system
    • function
      • can reproduce to create offspring of various types in subsequent generations
        • non-transgene homozygous
        • transgene homozygous
        • transgene heterozygous
  • Cre-lox system
    • construction
      • a system that allows turning on/off of gene of interest with an antibiotic-controlled promoter
    • function
      • to study a gene whose deletion is lethal to embryos
        • allows the embryo to develop to a certain stage and can then turn off a certain gene
      • can also study the timing of when a gene is important in development
  • RNAi 
    • construction
      • dsRNA is synthesized complementary to the mRNA sequence of interest
      • transfected into cells
      • dsRNA separates and binds the complementary mRNA
      • dsRNA (where one strand is the host mRNA) is seen as a viral product and degraded
    • function
      • ↓ expression of a particular gene

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