DNA repair

Question 1

systems
are vital to the survival of all organisms.

is a multistep process.

Answer 1

DNA repair

Question 2

recognizes thymine dimers
and splits them, which returns the DNA to
its original condition

Answer 2

Photolyase-

Question 3

Contains two light-sensitive cofactors.
The repair mechanism
| itself requires light
and is known as

Answer 3

photoreactivation.

Question 4

This process directly restores the
structure of DNA.

Answer 4

DIRECT REPAIR

Question 5

can remove methyl or
ethyl groups from guanine bases that
have been mutagenized by alkylating
agents such as nitrogen mustard and
EMS.

Answer 5

Alkyltransferase-

Question 6

were never used in
warfare. HN-1 originally was designed to
remove warts but was later found to be a
potential chemical warfare agent.

Answer 6

Nitrogen mustards-

Question 7

is a volatile organic solvent
that is mutagenic and carcinogenic.

Answer 7

Ethylmethanesulfonate (EMS,

Question 8

can precisely recognize a site in the DNA
where an abnormal base is located.

Answer 8

DNA N-glycosylases-

Question 9

is particularly important for the repair of oxidative DNA
damage.

Answer 9

BASE EXCISION REPAIR

Question 10

Primarily responsible for eliminating non-helix-distorting
changes that affect the structure of individual bases.

Answer 10

BASE EXCISION REPAIR

Question 11

which makes a cut (a nick) in the
DNA backbone on the 5′ side of the site.

Answer 11

AP endonuclease,

Question 12

removes a DNA segment
containing the abnormal region and, at the same time,
replaces it with normal nucleotides.

Answer 12

E. coli and DNA polymerase I,

Question 13

has the enzymatic ability to remove a
site that is missing a base, and then insert a nucleotide
with the correct base

Answer 13

DNA polymerase β(beta)

Question 14

can synthesize a short segment of
DNA, which displaces a short segment

Answer 14

• DNA polymerase δ(delta)or ε(epsilon)

Question 15

The flap is then removed by

Answer 15

flap endonuclease

Question 16

Often used to repair bulky, helix-distorting lesions.

Answer 16

NUCLEOTIDE EXCISION REPAIR

Question 17

is found in all eukaryotes and prokaryotes

Answer 17

NUCLEOTIDE EXCISION REPAIR

Question 18

DNA double helix obeys the AT/GC rule of
base pairing.

Answer 18

MISMATCH REPAIR

Question 19

is a base
pair mismatch in the DNA, not an abnormal nucleotide.

Answer 19

DNA defect

Question 20

• perhaps the most
  dangerous.

Answer 20

DNA double-strand break (DSB)

Question 21

This processing event is followed by the exchange of DNA
strands between the broken and unbroken sister
chromatids.

Answer 21

HOMOLOGOUS RECOMBINATION REPAIR

Question 22

The strands
of a normal sister chromatid are used to repair a damaged
sister chromatid.

Answer 22

HOMOLOGOUS RECOMBINATION REPAIR

Question 23

they are broken and then rejoined in a way that produces
separate chromatids.

Answer 23

crisscrossed strands

Question 24

• The two broken ends of DNA are simply pieced back
  together

Answer 24

NONHOMOLOGOUS END JOINING

Question 25

Frequently involves drugs that interfere with DNA synthesis

Answer 25

CANCER CHEMOTHERAPY

Question 26

prevents the formation of tetrahydrofolate

Answer 26

Methotrexate-

Question 27

contains a series of rings that intercalate between the DNA base pairs, such that DNA cannot act as a template during replication or transcription

Answer 27

Adriamycin-

Question 28

inhibits topoisomerase

Answer 28

Etoposide-