BIOL 200

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BIOL 200
2012-09-22 23:53:34

6th lecture
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  1. Mutation 
    Permanent, transmissibe chanes to the genetic material of a cell (or organism)
  2. Mutagen 
    Are chemical compounds, ultraviolet (UV) radiation or ionizig radiation (eg. xrays and atomic particles) that increased the frequency of mutations
  3. Carcinogens 
    agents thay cause cancer. All carcinogens are mutagens. Cause developmental mutations in the DNA 
  4. Some DNA polymerases have aproofreading activity, like which one?
    In eukaryotes, DNA polymerase δ, and not α, has a 3’ to 5’ exonuclease or “proofreading” activity
  5. Base Excision Repair
    1. DNA glycosylase hydrolyzes the bond between the mispaired base and the sugar phosphate backbone

    2.Apurinic/apyrimidinic endonuclease 1 (APE1)cuts the DNA backbone

    3. AP lyase associated with DNA polymerase β removes the deoxyribose phosphate  

    4. DNA polymerase β fills the gap and DNAligase seals the nickin the sugar phosphate backbone
  6. Cytosine can be methylated into?
    gene regulationtransposon (“jumping genes”) silencing chromatin remodeling
  7. Mismatch Excision Repair
    • Error incorporated into newly synthesized strand
    • 1. MSH2 and MSH6 bind to daughter strand 

    2.Triggers binding andactivity of MLH1 endonuclease (dimerized w/ PMS2)

    3.DNA helicase unwindsand DNA exonuclease digests segment of daughter strand

    4. Gap repair by Pol δ and DNA ligase
  8. Nucleotide Excision Repair
    1. 23B- activates XP-C

    2. Complex factor with TFIIH  and RPA binds to XP-G and a bubble is formed

    3. Cut huge part out
  9. Double-strand Break Repair by Endjoining
    1.Error-prone and can actuallyintroduce mutations

    2.A complex formed by DNA dependent protein kinase(DNA-PK) and Ku80/Ku70heterodimer binds to the ends of the break

    3.Ends are digested bynucleases

    4.Ends are ligated together