28

Question 1

DSB

Answer 1

double stranded breaks

Question 2

what causes DSB

Answer 2

principle cytotoxic lesion for ionizing radiation and radio mimetic chemicals

or mechanical stress on chromosomes or when DNA pol encounters DNA ss break or other type of DNA lesion

inaccurate repair of these can lead to mutations or genomic instability

tumorgenic potential
can induce appoptosis

Question 3

occur as intermediates in biological events just as V(D)J recombination in developing lymphoid cells

Answer 3

DSB

Question 4

mechanisms for repairing dsDNA breaks

Answer 4

non homologous end joinign (NHEJ)
homology directed repair- gene conversion
homology directed repair- homologous recombination

Question 5

dna seq info copies from one place to another

Answer 5

homology directed repair- gene conversion

Question 6

dna segments are exchagned

Answer 6

homology directed repair- homologous recombination

Question 7

exchanges DNA
rseutls in new genetic combinations in meiosis, conjugation, transduction, and transformation

Answer 7

homologous remcombination

Question 8

copies DNA from elsewhere in the genome

Answer 8

homology directed repair

Question 9

any mechanism of recombination has to include the followign

Answer 9

DNA synth
generation of regions of heteroduplex DNA

Question 10

what initiates homologous recombination and homology directed repari

Answer 10

ds break and resection

Question 11

what causes ds breaks

Answer 11

endonucleases or damage

Question 12

yeas ds break

Answer 12

HO endonuclease

Question 13

removal of DNA in one strand due to action of 5’-3’ exonuclease

Answer 13

resection

Question 14

bacteria resection

Answer 14

RecBCD

Question 15

yeast resection

Answer 15

MRX exonuclease

Question 16

human resection

Answer 16

MRN econuclease

Question 17

what binds to single starnd ends

Answer 17

strand exchange recombinases

Question 18

strand exchange recombinases examples

Answer 18

RecA (bact)
Rad51(Euk)
Dmc(meiosis specific)

Question 19

what do recombinase bound single strands do

Answer 19

invade the homologous duplex (second copy of molecule )
forms D loop
leaving us with a substrate for DNA synth

DNA synthesized using invading strand as a primer

Question 20

what happnes in homologus recombination

Answer 20

unpaired strand in D loop is captured by the othe end of the resectioned break and DNA synth can occur there

POINT OF DIFF BQ GENE CONVERSION AND HOMOLOGOUS RECOMBINATION

Question 21

outcome of homologous recombination

Answer 21

two intat dsDNA molecules joined by holiday junctions

Question 22

ways of resolving holiday junctions determine

Answer 22

whether or not recmombination occurs

Question 23

resolving two junctions in the same direction

Answer 23

no recombination occurs
A and B still on same moecule
heteroduplex non recmbinants are formed

Question 24

resolving two junctions in different directions

Answer 24

recombinant molecules are generateed

A and B on diffferent moelcuels

heteroduplex recombiannts are formed

Question 25

holiday funcions are a feature of

Answer 25

homologous recombination

Question 26

involve unequal crossing over

Answer 26

homologous recombinants

Question 27

what is required for homologous recombination

Answer 27

DNA synth

Question 28

what is required for homology directed repair

Answer 28

newly synth DNA is captured by other end of the resectioned break

Question 29

what is required for homology directed repair

Answer 29

newly synth DNA is captured by other end of the resectioned break further DNA synth compeltes the repari and results in gene conversion

Question 30

key difference in homology directied reapir and homologous recombination

Answer 30

what happnes at the second end of the ds break

Question 31

second end of the ds break in homology directed repair

Answer 31

capures newly synth DNA prmimed from the first end- two duplexes are not linked

Question 32

second end of DS break in homologous recombination

Answer 32

captures displced strand of the D loop- two duplexes are linked

Question 33

what do disease causing microorganisms use

Answer 33

gene conversion to change their cell surface entigens adn invade host immune response

Question 34

bacteria that use gene conversion to invde immune

Answer 34

gonorrhoae and lume disease

Question 35

borrelia burgdorferi

Answer 35

lyme disease

Question 36

neisseria gonorhoea

Answer 36

gonorheae

Question 37

how are the 3' overhanging end left at MAT following OH endonuclease cleaveag processed

Answer 37

by a 5' to 3' acting exonuclease the products of RAD50 MRE11 XRS2 genes to produce long ss3' tails that inteact with recombination producing RAD51 gene creates gene product that searched for homologous DNA seq

Question 38

what is sufficient to carry out strand exchange reactions in vivio

Answer 38

either RecA or Rad51 are sufficient

Question 39

what is sufficient to carry out strand exchange reactions in vivo

Answer 39

other proteins that are not jsut RecA and Rad51 needed to prevent secondary DNA structure impeding the reaction

Question 40

what are the accesory proteins needed in vivo for strand exchagne recations

Answer 40

BRCA1 and BRCA2- accesory proteins

Question 41

what do defects in the two BRCA genes lead to

Answer 41

predisopose inidividuals to breast and ovarian cancers

Question 42

BRCA1 function

Answer 42

ubiquitin ligase recruited early to dsDNA breaks recruits BRCA2

Question 43

BRCA2 functions

Answer 43

promotes binding of Rad51 to ssDNA and inhibits it binding to dsDNA interaction of BRC4 domain with Rad51 is blocked in families with predisposition to breast cancer

Question 44

what does BRCA1 from

Answer 44

multiple transcriptional complexes with ability to both corepress and coactivate genes involved diff processes