Microbiology 351 Exam 1 Flashcards - Set 18

DNA repair is divided into two types:
1. _____-_____ repair pathways, which prevent mutations
2. ____-_____ repair pathways, which risk introducing mutations

_____-_____ DNA repair pathways include: methyl mismatch repair, photoreactivation, nucleotide excision repair, base excision repair, and recobinational repair

____-____ DNA repair pathways operate only when damage is so severe that the cell has no other choice but to die.

______ _______ repair is based on recognition of the mehtylation pattern in DNA bases.

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.

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.

A bacterial strain with a high mutation rate is called _____ strain.

_______ is a type of error-proof repair pathway which involves the enzyme photolyase biding to the pyrimidine dimer and cleaving the cyclobutane ring.

_____ _____ 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)

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 results in an abasic site, or AP site (______ or ______), which can be recognized and cleaved by a specific AP endonuclease.

During base excision repair, the AP site allows ___ ____ __ to synthesize a replacement strand containing the proper base.

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

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"

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