DNA expression

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DNA expression
2011-01-23 15:55:30
DNA expression

DNA expression
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  1. What is the sequence of genes on the lac operon from 5' to 3'?
    Lac I(repressor gene); promoter;operator;lac Z;lac Y; Lac A
  2. What role does cap binding protein play? when is it active?
    when lactose is present, cap binding protein binds cAMP and binds to promoter region allowing polymerase to transcribe the structural genes
  3. How is the lac operon induced?
    lactose--> allolactose..binds repressor protein bound to operator region...adenylyl cyclase produces cAMP which binds cap binding protein, together they allow pol to transcribe the genes
  4. When is adenylyl cyclase active in the context of lac operon?
    when glucose is absent
  5. What happens in the presence of glucose and lactose?
    small if any transcription occurs bc cAMP is not active bc of glucose so cap binding protein cant bind to the promoter
  6. The stringent response in E. Coli is to what?
    a.a strarvation
  7. What happens during the stringent response?
    • during a.a starvation, an uncharged tRNA binds to A site of 70 S ribosome which induces phophorylation of GDP
    • phosphorylated GDP inhibits rRNA, tRNA and mRNA synthesis
  8. How is the synthesis of prokaryotic ribosomal proteins controlled?
    one of the ribosomal proteins binds to the shine dalgarno sequence of the ribosomal mRNA thus inhibiting the binding of the small rRNA to the mRNA--blocking transcription
  9. Trans acting molecules in eurkaryotic cells need to have what domains?
    • DNA binding domain
    • Transcription activating domain
  10. In the lac operon, which molecule acts as a trans-activating factor?
    repressor protein bc it has its own promoter and is constitutively expressed
  11. How does a steroid hormone affect transcrption?
    • steroid binds to an intracellular receptor(GR-Glucocorticoid receptor)
    • upon binding, conformation changes to zinger finger
    • which allows it to bind to Glucocorticoid regulatory element on the DNA which along with coactivator proteins inititates transcrption
  12. How does a membrane binding hormone( insulin, epinephrine) affect transcrption?
    upon binding a g protein, adenylyl cyclase produces cAMP which phosphorylates CREB which changes its conformation to a leucine zipper protein which binds to CRE
  13. Whats responsible for production of apolipoprotein B
    RNA editing where a truncated apolipoprotein B-48 is made in the intestine whereas in the liver you apolipoprotein-B 100
  14. What happens to the TfR mRNA in presence of High Fe?
    Apoferritin mRNA?
    • IRP binds Fe and IRE for TfR is vacant so it is degraded
    • IRP does not bind the IRE the Apoferritin mRNA so it is stable and stores excess Fe in the cell
  15. What happens to the TfR mRNA in presence of low Fe?
    Apoferritin mRNA?
    • IRP binds IRE of TfR stablizing it and producing iron receptors
    • IRP binds IRE of Apoferritin mRNA degrading it, preventing storage of Iron
  16. What are the steps of RNAi?
    Dicer(endonuclease) breaks dsRNA into ssRNA. ssRNA associates RISC complex and cleave targeted mRNA via an endonuclease(slicer)
  17. phosphorylation or dephosphorylation of eIF-2 hibits translation?
  18. Kinases that phosphorylate eIF-2 are activated by what environmental factors?
    Heme deficiency, a.a starvation and accumulation of misfolded proteins
  19. Acetylation of histones has what effect on a particular sequence of DNA?
    Upregulates expression
  20. Methylation of CG islands has what effect on DNA expression?
    Upregulates expression
  21. Whats one drug that leads to Gene amplification?
  22. What are 2 diseases that result from transposon movement?
    • hemophilia A
    • Duchene muscular dystrophy
    • Bothe X-linked recessive