Microbiology 351 Exam 1 Flashcards - Set 18

  1. DNA repair is divided into two types:
    1. _____-_____ repair pathways, which prevent mutations
    2. ____-_____ repair pathways, which risk introducing mutations
    • 1. Error-proof
    • 2. Error-prone
  2. _____-_____ DNA repair pathways include: methyl mismatch repair, photoreactivation, nucleotide excision repair, base excision repair, and recobinational repair
  3. ____-____ DNA repair pathways operate only when damage is so severe that the cell has no other choice but to die.
  4. ______ _______ repair is based on recognition of the mehtylation pattern in DNA bases.
    Methyl mismatch repair
  5. Methyl mismatch repair uses methylation of the ______ strand to discriminate from newly replicated DNA under the premise that this strand will contain the proper DNA sequence.
  6. The methyl-directed mismatch repair proteins (and genes) are called ____ because a high mutation rate results in strains that are defective in one of these proteins.
  7. A bacterial strain with a high mutation rate is called _____ strain.
  8. _______ is a type of error-proof repair pathway which involves the enzyme photolyase biding to the pyrimidine dimer and cleaving the cyclobutane ring.
  9. _____ _____ repair is a type of error-proof repair pathway which involves an endonuclease removing a patch of single-stranded DNA containing certain types of damaged bases, including dimers. (Uvr proteins)
    Nucleotide excision
  10. Name the type of error-proof repair pathway:
    - specialized enzymes can recognize specific damages bases and remove them without breaking the phosphodiester bonds
    Base excision repair
  11. Base excision repair results in an abasic site, or AP site (______ or ______), which can be recognized and cleaved by a specific AP endonuclease.
    apurinic, apyrimidinic
  12. During base excision repair, the AP site allows ___ ____ __ to synthesize a replacement strand containing the proper base.
    DNA Pol I
  13. Name the error-proof repair pathway;
    - takes place at the replication fork
    - a single-stranded segment of the undamaged daughter strand can be used to replace a gap in the damaged daughter strand, which is carried out by RecA
    - Not limited to pyrimidine dimers
      - It will work on any damage that causes gaps during replication
    Recombinational repair
  14. Name the error-prone DNA repair:
    - induced by extensive DNA damage
    - RecA coprotease activity stimulates autodigestion of the LexA repressor
    - Expression of many DNA repair enzymes
      - Among them, two "sloppy" DNA polymerases that lack proofreading activity, however the cell has no other option but "mutate or die"
    SOS ("Save Our Ship") repair
  15. Name the error-prone DNA repair:
    - common in eukaryotes
    - found in some bacteria such as Mycobacterium and Bacillus
    - May cause loss or addition of a few nucleotides or even the joining of two previously unlinked DNA molecules
    Nonhomologous end joining (NHEJ)
Card Set
Microbiology 351 Exam 1 Flashcards - Set 18
DNA Repair and Mobile Genetic Elements