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EOM 1 - Test 2 > Sollars - DNA Replication I (Prokaryotes) > Flashcards

Sollars - DNA Replication I (Prokaryotes) Flashcards

1
Q

What are the three rules of DNA Replication?

A
  1. DNA Replication is semiconservative 2. Replication begins at an Orgin, proceeds bidirectionally 3. DNA synthesis proceeds in a 5’ - 3’ direction and is semi continuous
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2
Q

What does each daughter cell duplex consist of?

A

One parental strand and one newly synthesized strand

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3
Q

Where are origins usually found–why?

A

Around A-T base pairs due to weaker hydrogen bonding compared to G-C (2 vs 3)

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4
Q

Which end are deoxynucleotides added to growing chains?

A

3’ end

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5
Q

What initiates strands during DNA synthesis?

A

RNA primers

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6
Q

Synthesis of the leading strand is ______? Synthesis of the lagging strand is ______?

A

Continuous Discontinuous

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7
Q

What are the three steps of initiation?

A
  1. DNA-A binds origin of replication
  2. Helicase dissociates helix
  3. ssDNA binding proteins keep DNA from reannealing
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8
Q

What does elongation require?

What enzyme grows leading strand?

What is the orientation compared to the parent strand?

A

RNA primers

DNA Polymerase III; works in 5’-3’ direction; beginning at the 3’ end of each RNA primer

Complimentary and antiparallel to the parent template

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9
Q

How is the lagging strand synthesized in DNA synthesis?

A

Small Okazaki Fragments

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10
Q

What initiates Okazaki Fragments?

What completes them?

A

RNA Primer Synthesis by Primase

Completed by DNA Polymerase III, made in a 5’ - 3’ direction

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11
Q

What molecule class alleviates supercoiling strain via nicks and repairing nicks?

A

Topoisomerases

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12
Q

When does proofreading occur?

What does it ensure?

A

Elongation

Ensures fidelity

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13
Q

If DNA Polymerase mismatches a nucleotide–how does proofreading occur?

A

3’-5’ Exonuclease activity to excise the mismatched nucleotide;

occurs bia enzyme backing up

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14
Q

DNA Polymerase I

A

Removes RNA primers

Special 5’-3’ Exonuclease Activity

Proofreading

DNA Repair

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15
Q

DNA Polymerase II

A

DNA repair

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16
Q

DNA Polymerase III

A

Latches on, stays on

Synthesizes most DNA during leading and lagging strands

Proofreading

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17
Q

DNA Polymerase IV, V

A

DNA Repair

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18
Q

What three methods is genetic fidelity preserved?

A
  1. Geometry - Active site of DNA Polymerase; must have 3 rings… tautomerization causes problems
  2. Proofreading; 3’-5’ Exonuclease Activity
  3. Mismatch Repair and DNA Methylation - Parent strand methylated, copied not. Helps identify correction version to repair.
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19
Q

What does proofreading’s 3’-5’ Exonuclease activity preserve?

A

Fidelity

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20
Q

Why is the parent strand methylated and copied not?

A

Helps identify correct version to repair

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23
Q

What is the 1st rule of DNA replication?

A

DNA replication is semiconservative; each parental strand is used as a template for the synthesis of a new complementary strand

24
Q

What does the first rule state a daughter cell will receive?

A

One of the two identical DNA molecules

25
What does each daughter duplex consist of?
One parental strand, and one newly synthesized strand
26
What is conservative replication?
Both templates go on to the same cell
27
Where are origins of replication found and why?
Sites rich in A-T, due to weaker hydrogen bonding (2vs3) than G-C pairing
28
What direction do replication forks move from the origin of replication?
Bidirectional
29
What is the 2nd law of DNA replication?
Replication begins at an origin, and proceeds bidirectionally
30
What is the 3rd rule of DNA replication?
DNA synthesis proceeds in a 5'-3' direction, and is semi-discontinuous
31
Where are new deoxynucleotides added to the growing chain?
3' end
32
What initiates each new DNA strand during replication?
RNA primer
33
How is synthesis of the leading vs lagging strand?
Leading = continuousLagging = discontinuous
34
AAA+ ATPases
DnaA binds to the origin of replication and disassociates the helical strands; energy of ATP cleavage is used to produce conformational change in DnaA, which forces the strands apart
35
DNA Ligase
Creates phosphodiester bonds by using the energy of ATP cleavage, to seal "nicks" in the DNA strand
36
DNA Polymerase
"Workhorse" enzyme; responsible for strand elongation, require ssDNA template AND RNA primer
37
Helicase
Cause disassociation of the two strands of the double helix, unwinding the structure using energy released from ATP cleavage
38
Nucleases
Sever phosphodiester bonds of the DNA backbones; two types--exo/endo nuclease
39
Primase
Responsible for synthesizing short stretches of RNA complementary to the template DNA strand that serve as primer
40
TopoisomeraseWhat additional functions do they contain?What is difference in Type I and Type II
Adjusts supercoiling of DNA double helices, both alleviating stress and introducing negative supercoiling. Endonuclease and Ligase (cut and seal) Type I = cleave one strand of double helixType II = cleave both strands of double helix
41
What occurs at Initiation?
1. DnaA binds the origin of replication2. Helicase breaks double helix3. ssDNA binding proteins maintain disassociation
42
Elongation is accompanied by what function to ensure proper base pairing?
Proofreading
43
What molecule is instrumental in alleviating supercoiling strain?
Topoisomerases
44
What initiates the Okazaki fragment?
Synthesis of an RNA primer by primase
45
What powers DNA synthesis?
dNTP to dNMP (2 Pi)
46
What is DNA gyrase?
Type II Topoisomerase
47
Topoisomerase II Poisons
Stabilize covalent DNA topoisomerase II complex
48
Catalytic Inhibitors
Topoisomerase II inhibitors (w/out stabilizing covalent complex)
49
When does proofreading occur and what does it ensure?
Elongation, fidelity
50
What enzyme excises the mismatched pair in proofreading?
3'-5' Exonuclease
51
When does termination occur?
When replication forks join up

EOM 1 - Test 2 (18 decks)

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