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Flashcards in DNA Repair Systems Deck (27):
1

Two examples of enzymes involved in direct repair of damaged bases.

DNA photolyase and O6-alkylguanine alkyltransferase

2

Why is O6 alkylG mutagenic

It can mispair with T resulting in a GC --> AT transition

3

What are the three major types of DNA repair systems?

Direct repair of damaged bases, excision repair, and mismatch repair

4

What are the two types of Excision repair?

Nucleotide excision repair and base excision repair

5

What is the difference between DNA photolyase and UvrAB complex?

DNA photolyase is light activated, breaks the dimer, limited penetration into the skin.

UvrABcomplex requires ATP, makes endonucleolytic cuts to REMOVE nucleotides, and does not need to be light activated, and repairs other types of damage

6

Nucleotide excision repair: Identifies the site of damage

UvrAB complex

7

Nucleotide excision repair: exinuclease that makes endonucleatic cuts (5' and 3') to the lesion

UvrBC

8

Nucleotide excision repair: unwinds and removes the excised piece

Helicase

9

Nucleotide excision repair: Fills the resultant gap

DNA pol I

10

Nucleotide excision repair: seals the nick in the backbone

DNA ligase

11

Featured enzyme of Base Excision Repair

DNA-N-Glycosylases

12

How do DNA-N-Glycosylases work?

They specifically recognize incorrect bases in DNA and remove them by creating apurinic or apyrimidinic sites.

13

Base excision repair: A mismatched uracil is identified by_________ , which cleaves the base from the ____ _______ to create an _______ site.

Uracil-DNA glycosylase, DNA backbone, apyrimidinic site

14

Base excision repair: removes the sugar residue from the backbone. Where does this enzyme cleave the backbone relative to the site?

Endonuclease, 5'

15

Base excision repair: enzyme that removes the damaged region plus a few more nucleotides. What activity of this enzyme is used?

DNA Pol I, 5' exonuclease activity

16

Base excision repair: fills the gap

DNA pol I

17

Base excision repair: closes the nick in the backbone

DNA ligase

18

Which repair systems require ATP?

Nucleotide excision repair and mismatch repair

19

Which repair system directly scans for methylated strand?

Mismatch repair

20

Carries out methyl-directed mismatch repair

MutHLS system

21

Mismatch repair: binds to DNA at the site of mismatch. Followed by two others called:

MutS; MutL and Mut H

22

Mismatch repair: using ATP hydrolysis for energy, it pulls DNA in from both directions until reaching a sequence on the template strand. What is this sequence?

Must S, GATC

23

Mismatch repair: cleaves the unmethylated DNA strand 5' to the G in the GATC sequence that is mirrored in the new strand.

MutH endonuclease

24

Mismatch repair: unwinds the DNA back past the mismatch

DNA helicase II

25

Mismatch repair: removes the damaged DNA

exonuclease

26

Mismatch repair: Fills the gap

DNA pol III

27

Mismatch repair: seals the nick

DNA ligase