DNA Damage and Repair

Question 1

The chemical nature of DNA makes it highly susceptible to ______

Answer 1

damage

Question 2

distortions to the shape of the DNA helix facilitates recognition of DNA _______

Answer 2

lesions

Question 3

DNA replication is prone to ______ and enzymes can
accidentally remove or add a base (examples… ______ and ________)

Answer 3

error, cystic
fibrosis, Tay-Sachs disease

Question 4

________ DNA damage are caused by environmental or external factors

Answer 4

exogenous

Question 5

_______ DNA damage is caused by internal processes within the cell

Answer 5

endogenous

Question 6

Cancer and aging are a
consequence of
unrepaired or faulty ______

Answer 6

DNA repair

Question 7

DNA polymerase gama functions during DNA replication in ______

Answer 7

mitochondria

Question 8

DNA polymerase delta functions in replication by synthesizing the ______ strand and helping with DNA ______

Answer 8

lagging, repair

Question 9

DNA polymerase epsilon functions in replication by synthesizing the ______ strand

Answer 9

leading

Question 10

cell cycle checkpoint proteins are an important factor in the consequences of ______

Answer 10

DNA damage

Question 11

DNA damage will cause a delay in _______

Answer 11

cell cycle progression

Question 12

check point 1 will prevent a cell from entering into ____ phase if its DNA contains damage

Answer 12

S

Question 13

check point 2 will prevent a cell from entering
into _____ phase if there are breaks or damage sites in the DNA

Answer 13

M

Question 14

_______ and _______ are caused by oxidation and alkylation of the DNA

Answer 14

single stranded breaks, oxidized bases

Question 15

______ and ______ are caused by UV light and anti-tumor drugs

Answer 15

bulky lesions, cross links

Question 16

mismatches in DNA is caused by ______

Answer 16

replication errors

Question 17

_______ are caused by irradiation, anti-tumor drugs and replication fork collapse

Answer 17

double stranded breaks

Question 18

________ is a type of spontaneous DNA damage that causes an unnatural DNA base change from C to U that will be carried over into DNA replication

Answer 18

deamination of cytosine

Question 19

________ is a type of spontaneous DNA damage will cause a base change to thymine which will escape DNA repair

Answer 19

deamination of 5-methyl cytosine

Question 20

_______ is a type of spontaneous DNA damage where the base of a nucleotide is cleaved causing the nucleotide to be missing a nitrogenous base

Answer 20

depurination

Question 21

_______ is the addition of a methyl or ethyl group to DNA bases

Answer 21

alkylation

Question 22

tobacco specific nitrosamines will be metabolized by the liver and lungs and will then base pair to DNA causing a base that is ______ which creates problems during ______

Answer 22

too bulky, DNA replication

Question 23

tobacco specific dimethylnitrosamine is a carcinogen that is metabolized by the liver which causes a methyl group to be transferred to _____ this _______ now base pairs with thymine causing a permanent A:T mutation

Answer 23

guanine, O6-methyl-gunaine

Question 24

smoking can cause many types of alkylated DNA including ________, _______, _______ crosslinking, and _______ crosslinking

Answer 24

monoalkylation, intercalation, interstrand, intrastrand

Question 25

DNA damage by oxidation targets guanine and creates a OxoG which basepairs with C but also basepairs with A causing a _______

Answer 25

mismatched pairing

Question 26

oxidation of aromatic polycyclic benzo[a]pyrene in cells causes covalent binding to _______ residues in DNA and interrupts H bonding in G-C pairs which forms ______

Answer 26

guanine, bulky adducts

Question 27

DNA damage by ___________ causes the formation of adjacent pyrimidine dimers, the formation of covalent dimers on the C=C double bonds and the defective base pairings stops replication and transcription

Answer 27

Ultraviolet UV irradiation

Question 28

blue light irradiation generates __________ and induces oxidative stress in oral tissues and the eyes however some oxidative stress is counteracted by antioxidants and DNA repair mechanisms

Answer 28

reactive oxidative species

Question 29

__________ are the most lethal types of DNA damage

Answer 29

double stranded breaks

Question 30

double stranded breaks are caused by ______ and ______

Answer 30

gamma irradiation, X-ray

Question 31

if double stranded breaks are left unrepaired, this can lead to the breakdown of ________ and ________ as well as interferes with DNA replication and transcription

Answer 31

chromosomes, chromosomal rearrangements

Question 32

the indirect effects of gamma irradiation and X-rays include production of _______ that cause single strand breaks and abasic sites

Answer 32

ROS

Question 33

the direct effects of gamma irradiation and X-rays include ______ and _______

Answer 33

single, double strand breaks

Question 34

Base excision repair repairs _____, ______, ______ and _______

Answer 34

Uracil, OxoG, O6-methyl-G, single strand breaks

Question 35

the steps of base excision repair include the removal and replacement of modified ______, DNA glycoslyase binds DNA and removes damaged ______, AP endonuclease nicks the _______ and DNA polymerase _______ the gap then ligase ______ the nicks

Answer 35

bases, base, backbone, fills in, seals

Question 36

nucleotide excision repair repairs _______ and ______ caused by chemicals

Answer 36

pyrimidine dimers, bulky adducts

Question 37

the steps of nucleotide excision repair include the scanning of DNA for damage, a pair of coordinated incisions by _______ on either side of the DNA strand carrying the lesion, ______ removes the single strand segment with the lesion, ________ will fill in the gaps and _____ will seal the gaps

Answer 37

DNA nucleases, helicase, DNA polymerase, ligase

Question 38

individuals with xeroderma pigmentosum are unable to perform ____---

Answer 38

nucleotide excision repair

Question 39

transcription coupled excision repair is nucleotide excision repair coupled with ______

Answer 39

RNA transcription

Question 40

transcription coupled excision repair ensures the transcribed DNA strand of an active gene is repaired faster, where RNA polymerase senses damage and _______ to trigger the recruitment of ______ protein to next recruit components of _____

Answer 40

stalls itself, CSB, NER

Question 41

direct repair refers to mechanisms that remove damage directly without ______ or ______ of segments of DNA

Answer 41

cutting, rearranging

Question 42

DNA photlyases are photoreactivated enzymes that use visible light to cleave ______ dimers

Answer 42

pyrimidine

Question 43

methyl transferases are adaptive response enzymes that transfer a _______ group from O6-guanine to a _______ residue within the protein

Answer 43

methyl, cysteine

Question 44

direct repair of pyrimidine dimers, not found in humans, uses _______ to cleave clyclobutane ring

Answer 44

DNA photolyase

Question 45

direct repair of O6-methylguanine uses _________ to bind and take away the added methyl group from guanine

Answer 45

methyltransferases

Question 46

double stranded breaks are repaired using __________, __________ and ________

Answer 46

homologous recombination, non-homologous end joining, alternative NHEJ

Question 47

double strand break repair repairs double strand breaks as well as _______, _____ and _____ strand crosslinks

Answer 47

single strand breaks, inter, intra

Question 48

homologous recombination uses the _______ and the _______ to repair the broken ends

Answer 48

intact sister chromatid, homologous chromosome

Question 49

BRCA1 and BRCA2 are critical for homologous recombination in recruiting specific _____ to bind to the broken ends

Answer 49

proteins

Question 50

homologous recombination is only available at ________

Answer 50

S and G2 phase before mitosis

Question 51

non-homologous end joining and alternative non-homologous end joining directly ______ broken ends, but DNA information is _____

Answer 51

ligates, lost

Question 52

lesion by-pass (translesion) DNA synthesis is used when a damaged nucleotide was not repaired before _______, a translesion DNA polymerase allows for DNA replication to continue but does _________ causing mutations and high error prone base pairing

Answer 52

DNA replication, not repair lesion

Question 53

mismatch repair mechanism corrects _______ in DNA that were caused by DNA polymerase

Answer 53

mismatched bases

Question 54

mismatch repair mechanism starts with cutting of the ________ synthesized DNA strand, excise the _______, resynthesize the DNA and ______ the patch to the continuous DNA strand

Answer 54

unmethylated most recently, mismatched base, ligate