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Flashcards in DNA Replication And Repair Deck (47)
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1
Q
What direction does DNA replication proceed?
A
5' to 3' direction
2
Q
Leading strand
A
DNA is replicated in one smooth, continuous process
3
Q
Lagging strand
A
DNA is replicated in small sections then fused together
4
Q
Primers
A
Short section of RNA which is complementary to the template strand and contains free 3' OH group
5
Q
Helicase
A
Separates the DNA strands. Requires ATP.
6
Q
What reaction does DNA polymerase catalyze?
A
Hydrolysis of PPi to 2Pi that allows the incoming nucleotide to be bound to the strand.
7
Q
Primase
A
RNA polymerase that is required to initiate DNA synthsis
8
Q
Okazaki Fragments
A
Short sections of primer RNA plus DNA that form on the lagging strand. Will be joined together later.
9
Q
Replisome
A
Total proteins and enzymes required for DNA synthesis at a replication fork
10
Q
Topoisomerases
A
Acts to prevent the extreme supercoiling of the parental helix by breaking and rejoining DNA chains. Relieves the tension ahead of the replication fork.
11
Q
Type I topoisomerase
A
Makes a break/nick in a strand of DNA helix, passes the other strand thru the break to relax the coil. Removes 1 supercoil
12
Q
Type II topoisomerases
A
Requires ATP. *AKA DNA gyrase in E. Coli* Produce break in BOTH strands of DNA. 2 supercoils are removed in one step
13
Q
Single Stranded binding protein
A
Keeps the separated strands as single strands. Are displaced and reused as DNA is replicated
14
Q
DNA polymerase I
A
Removes RNA primers (5' ā€“> 3' exonuclease activity) and fills in gaps with dNTP that matches the exposed DNA template. Edits/proofreads the strand (3'->5' exonuclease activity), cleaving off any unpaired 3' terminal nucleotide
15
Q
DNA polymerase III
A
Major replicative enzyme. Stays on the DNA molecule for long stretches of processing
16
Q
DNA ligase
A
Enzyme that catalyzes formation of phosphodiester bond b/t 2 Okazaki fragments
17
Q
Types of DNA mutations
A
Point mutations, insertions, deletions
18
Q
Point mutations
A
substitution of one base for another
19
Q
Insertion
A
Adding one or more nucleotides within a DNA sequence
20
Q
Deletions
A
Removal of one or more nucleotides with a DNA sequence
21
Q
Steps of DNA repair
A
Removal, filling of the gap, ligation
22
Q
Nucleotide excision repair
A
Removal of a group of nucleotides
23
Q
Base excision repair
A
Specific glysosylase that removes a damaged base by hydrolyzing an N-glycosidic bond
24
Q
What serves as substrates in DNA synthesis?
A
Deoxyribonucleotide triphosphates
25
Q
What do DNA polymerases require for activity?
A
Primer and template
26
Q
Ciprofloxin
A
Works on both Gram - and + bacteria. Effects the supercoiling of bacterial DNA gyrase
27
Q
Replisome
A
All factors required for DNA synthesis
28
Q
What 4 classes of DNA polymerase are found in the nucleus?
A
Alpha, beta, delt, sigma
29
Q
Where is gamma DNA polymerase found?
A
mitochondria
30
Q
What 2 classes of DNA polymerase are involved in DNA repair?
A
beta and sigma
31
Q
What two chemical reactions are used to disassociate histones from DNA?
A
Acetylation and phosphorylation
32
Q
What proteins dictate the phase of replication that the cell is in?
A
Cyclins (A and E involved in DNA synthesis)
33
Q
What two types of agents cause DNA damage?
A
physical and chemical
34
Q
What causes thymine dimers to form?
A
UV rays
35
Q
Why does a thymine dimer cause disfunction in DNA?
A
Distorts the helix, so the DNA cannot be replicated without error
36
Q
What is deamination?
A
Cytosine converts to uracil, ultimately leading to a Cā†’T mutation
37
Q
Single Strand break
A
The phosphodiester bond is broken on a single strand of DNA, is easily repaired.
38
Q
Double strand break
A
2 single strand breaks occur near each other on opposite sides of the DNA. Is very hard to repair, and usually results in cell death
39
Q
When is excision repair used?
A
Used to repair bulky damages to DNA
40
Q
When is base excision repair used?
A
Small modifications to DNA bases
41
Q
Postreplication repair
A
is known as the SOS repair, error prone repair which occurs as a last ditch effort where a random nucleotide is inserted
42
Q
Xeroderma pigmentosum
A
Excision repair proteins have lost activity, so cannot repair damages, particularly those done by UV. Can have eye photosensitivity
43
Q
Ataxia Telangiectasia
A
Gamma irradiation sensitivity. Usually have lymphomas, Signs: ataxia, dilation of blood vessels in the skin, chromosomal aberrations
44
Q
Fanconi's Anemia
A
Have a sensitivity to cross linking. Causes leukemias. Signs: hypoplastic pancytopenia, congenital abnormalities
45
Q
Bloom's Syndrome
A
Sensitivity to UV. Causes leukemias. Signs: skin photosensitivity, usually a butterfly shaped rash on the face
46
Q
Cockayne's Syndrome
A
Have a sensitivity to UV. Causes various tumor cancers. Signs: neurological defects, dwarfism
47
Q
10% of colorectal cancers are cased by what defect?
A
Mismatch repair is defective