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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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21
Q
A
22
Q
A
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
Q

What does each daughter duplex consist of?

A

One parental strand, and one newly synthesized strand

26
Q

What is conservative replication?

A

Both templates go on to the same cell

27
Q

Where are origins of replication found and why?

A

Sites rich in A-T, due to weaker hydrogen bonding (2vs3) than G-C pairing

28
Q

What direction do replication forks move from the origin of replication?

A

Bidirectional

29
Q

What is the 2nd law of DNA replication?

A

Replication begins at an origin, and proceeds bidirectionally

30
Q

What is the 3rd rule of DNA replication?

A

DNA synthesis proceeds in a 5’-3’ direction, and is semi-discontinuous

31
Q

Where are new deoxynucleotides added to the growing chain?

A

3’ end

32
Q

What initiates each new DNA strand during replication?

A

RNA primer

33
Q

How is synthesis of the leading vs lagging strand?

A

Leading = continuousLagging = discontinuous

34
Q

AAA+ ATPases

A

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
Q

DNA Ligase

A

Creates phosphodiester bonds by using the energy of ATP cleavage, to seal “nicks” in the DNA strand

36
Q

DNA Polymerase

A

“Workhorse” enzyme; responsible for strand elongation, require ssDNA template AND RNA primer

37
Q

Helicase

A

Cause disassociation of the two strands of the double helix, unwinding the structure using energy released from ATP cleavage

38
Q

Nucleases

A

Sever phosphodiester bonds of the DNA backbones; two types–exo/endo nuclease

39
Q

Primase

A

Responsible for synthesizing short stretches of RNA complementary to the template DNA strand that serve as primer

40
Q

TopoisomeraseWhat additional functions do they contain?What is difference in Type I and Type II

A

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
Q

What occurs at Initiation?

A
  1. DnaA binds the origin of replication2. Helicase breaks double helix3. ssDNA binding proteins maintain disassociation
42
Q

Elongation is accompanied by what function to ensure proper base pairing?

A

Proofreading

43
Q

What molecule is instrumental in alleviating supercoiling strain?

A

Topoisomerases

44
Q

What initiates the Okazaki fragment?

A

Synthesis of an RNA primer by primase

45
Q

What powers DNA synthesis?

A

dNTP to dNMP (2 Pi)

46
Q

What is DNA gyrase?

A

Type II Topoisomerase

47
Q

Topoisomerase II Poisons

A

Stabilize covalent DNA topoisomerase II complex

48
Q

Catalytic Inhibitors

A

Topoisomerase II inhibitors (w/out stabilizing covalent complex)

49
Q

When does proofreading occur and what does it ensure?

A

Elongation, fidelity

50
Q

What enzyme excises the mismatched pair in proofreading?

A

3’-5’ Exonuclease

51
Q

When does termination occur?

A

When replication forks join up

EOM 1 - Test 2 (18 decks)

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