DNA Replication And Repair Flashcards

1
Q

What direction does DNA replication proceed?

A

5’ to 3’ direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Leading strand

A

DNA is replicated in one smooth, continuous process

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Lagging strand

A

DNA is replicated in small sections then fused together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Primers

A

Short section of RNA which is complementary to the template strand and contains free 3’ OH group

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Helicase

A

Separates the DNA strands. Requires ATP.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Primase

A

RNA polymerase that is required to initiate DNA synthsis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Okazaki Fragments

A

Short sections of primer RNA plus DNA that form on the lagging strand. Will be joined together later.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Replisome

A

Total proteins and enzymes required for DNA synthesis at a replication fork

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Single Stranded binding protein

A

Keeps the separated strands as single strands. Are displaced and reused as DNA is replicated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

DNA polymerase III

A

Major replicative enzyme. Stays on the DNA molecule for long stretches of processing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

DNA ligase

A

Enzyme that catalyzes formation of phosphodiester bond b/t 2 Okazaki fragments

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Types of DNA mutations

A

Point mutations, insertions, deletions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Point mutations

A

substitution of one base for another

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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