Bisc 320 Final

Front 1

Mismatch Repair

Back 1

Front 2

Endonuclease

Back 2

(nickase) cleaves DNA bonds within DNA molecules

Front 3

Exonuclease

Back 3

cleaves thenucleotides at the end of aDNA molecule, requires free3’ or 5’ –OH, works with ahelicase

Front 4

Mut H

Back 4

- endonuclease that creates a nick on the new strand of DNA in MR

- binds the nearest GATCmethylated sites andcuts only non-methylated DNA

Front 5

Intercalating agents

Back 5

Cause the addition of base pairs byslipping between the bases in the template strand

Front 6

Uvr

Back 6

genes for nucleotide excisionrepair - loss leads to UV sensitivity

Front 7

Rad

Back 7

genes for double-strand breakrepair - loss leads to radiationsensitivity

Front 8

Mut

Back 8

genes for mismatch repair -loss results in high mutation rate

Front 9

OxoG

Back 9

can be mispaired to A

Front 10

O6-methyl G

Back 10

can be mispaired to T

(BER)

Front 11

Base-Excision Repair

Back 11

one of two types of excision: acts on a single damaged nucleotide

(BER and DR)

1. DNA glycolysase recognizes and removes damaged base. 2 AP endonuclease recogs abasic site. 3. replacement via polymerase and ligase

Front 12

Hydrolytic Reactions

Back 12

-deamination of cytosine to uracil

-depurination leaves an abasic site

Front 13

DNA Glycolisase

Back 13

flips the damaged base to expose the damaged site that will be cleaved and removes it

Front 14

Damage Reversal (DR)

Back 14

-mostly in bacteria only

-degrades protein after process (enzyme is methylated and site is demethylated)

-uses methyltransferase to transfer methyl group from one substrate.

-focus on O6-methylG transferase

-very efficient yet consuming because methylated enzyme is degraded (sacrifice an entire protein)

Front 15

Trans-letion Synthesis (TLS)

Back 15

- allows damage, not repair

-flexible but causes mutation

- Uniquitination triggers the switch to a trans-lesionpolymerase in mammalian cells

- In E. Coli, Pol IV and V come in a and replace the stalled polymerase at the fork and incorporate random bases.

Front 16

RPA

Back 16

(Replication protein A)

damage sensor: single stranded binding protein that binds DNA ahead of the polymerase at the rep fork--->>> recruits ATR which phosphorylates H2AX

keeps the DNA unwound for repair/replication

Front 17

MRN

Back 17

damage sensor: recognizes DNA double strand breaks--->>> Recruits ATM which phosphorylates H2AX

Front 18

Swr1 and Ino80

Back 18

-chromatin remodelers

-promote strand invasion byproviding access to the donor sequence

Front 19

NHEJ

Back 19

-error prone, fast, G1

-doesnt require homology

-rejoines 2 ends

Front 20

Single Strand Annealing (SSA)

Back 20

Front 21

Alt-EJ

Back 21

Front 22

MRN-Ctip

Back 22

endonuclease that initiates resection in HR

works with wrn helicase

Front 23

Endonucleases that extends resection

Back 23

Dna2 (endonuclease)

blm (3'-5' helicase)

exo1 (exonuclease)

Front 24

Werner syndrome

Back 24

Cancer predisposition- Telomeric instability- Premature aging

due to Wrn mutation

Front 25

RecA/Rad51

Back 25

binds to ssDNA, replaces RPA, forms a filament around ssDNA and probes for homology (needs more than 15bp), and drives strand invasion

Front 26

Brca2

Back 26

-subs RPA with rad51

-mutation responsible for breast cancer

Front 27

RuvAB

Back 27

promotes Holliday Junction migration in bacteria only

RUV A recognizes holliday junctions

Ruv B helicase promotes movement

Ruv C resolves Holliday Junctions by cleaving acrossthe Junction

Front 28

Blm helicase & top3 isomerase

Back 28

requires for HJ dissolution

helicase can revert recombination intermediates by displacing rad51

topoisomerase activity counteracts positivesupercoiling during dissolution by creating breaks in the DNA to resolve topological issues

Front 29

CRISPR/Cas9

Back 29

-used as a research tool

-Cas9 can be directed to ANY target sequence toinduce DSBs and improve gene targeting