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Molecular Biology and Genetics > DNA Replication and Chromosomes: DNA replication > Flashcards

DNA Replication and Chromosomes: DNA replication Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Where does DNA replication occur?

A

In a cell.

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2
Q

Of what is DNA replication a part?

A

The cell cycle.

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3
Q

Which are critical aspects of cell biology?

A

The enzymes required for DNA replication, DNA mutation, and repair.
Cell cycle control.

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4
Q

What do the critical aspects of cell biology allow?

A

The development of modern molecular biology techniques.

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5
Q

For what is the replication of each chromosome required?

A

For each round of cell growth and division.

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6
Q

With what does the replication of chromosomes be tuned?

A

The replication of all other cell components and structures.

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7
Q

When does DNA synthesis occur?

A

During ‘S-phase; of Interphase of cell cycle.

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8
Q

Where does DNA synthesis result?

A

In duplicate copies of each chromosome before cell division in M-phase.

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9
Q

What did Watson and Crick suggested with their base-pairing model of DNA, in 1953?

A

A replication mechanism.

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10
Q

How was the replication mechanism termed later on?

A

Semi-conservative replication.

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11
Q

What was happening in the semi-conservative replication?

A

Parental DNA strands were separated and served as templates.

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12
Q

Why were the parental DNA strands separated and served as templates?

A

For the replication of new daughter strands.

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13
Q

Who did question the semi-conservative replication and suggested other mechanisms for DNA replication?

A

Delbruck and others.

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14
Q

How many theories about DNA replication were in 1957?

A

3.

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15
Q

Which were the 3 theories about DNA replication in 1957?

A
  1. Semi-conservative.
  2. Conservative.
  3. Dispersive replication.
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16
Q

Who did address the 3 theories of DNA replication, and how?

A

Meselson and Stahl, with experiments.

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17
Q

How were the experiments of Meselson and Stahl characterised?

A

The most beautiful experiment in biology.

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18
Q

What did Meselson and Stahl do in their experiment in 1958?

A

They grew Escherichia coli in 15N media for one generation –> transferred cells into 14N media –|> continued incubation.

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19
Q

What happened in the Meselson-Stahl experiment?

A

DNA isolated from samples.

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20
Q

What did Meselson and Stahl do once they managed to isolate DNA from E. coli samples with 15N and 14N with media?

A

Took DNA from cultures –> ultra-centrifuged DNA –> photographed –> scanned –> determined DNA concentrations in tubes.

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21
Q

What did 14N and 15N controls confirm?

A

Light and heavy DNA positions.

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22
Q

What did the Meselson-Stahl experiment confirm?

A

DNA was replicated in a semi-conservative manner.

Exactly what Watson and Crick said in 1953.

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23
Q

What is responsible for DNA replication in vivo?

A

A replication complex/’machine’.

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24
Q

What does a replication machine generate?

A

Copies of whole chromosomes in each cell cycle.

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25
Q

Where are some elements also involved in DNA synthesis?

A

In DNA repair.

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26
Q

With what is DNA repair associated?

A

With replication.

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27
Q

As what does DNA repair result?

A

As the DNA damage result.

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28
Q

What does DNA Topoisomerase do?

A

It cuts DNA.

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29
Q

Why does DNA Topoisomerase cut DNA?

A

To release supercoils and allow it to relax.

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30
Q

What does DNA Helicase do?

A

It unwinds and opens out the DNA duplex.

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31
Q

Why does DNA Helicase unwind and open out the DNA duplex?

A

To provide single-stranded regions.

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32
Q

What are the single-stranded regions?

A

The start-points for DNA replication.

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33
Q

How is single DNA strand replication characterised?

A

Simple.

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34
Q

How is replication of both strands of DNA at the same time, characterised?

A

Difficult.

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35
Q

Why is replication of both DNA strands at the same time difficult?

A

Because the DNA Polymerases will get in each other’s way.

36
Q

What does each strand replication need to avoid DNA Polymerases getting in each other’s way?

A

They need to tune with the other strand’s replication.

37
Q

What does Topoisomerase cut exactly of DNA?

A

The phosphodiester backbone of DNA of the double helix.

38
Q

Why does topoisomerase cut the phosphodiester backbone of the double helix of DNA?

A

To allow it be opened up without untwisting.

39
Q

What do type 1 topoisomerases relax?

A

Single-stranded DNA.

40
Q

What do type 2 topoisomerases relax?

A

Double-stranded DNA.

41
Q

How is E. coli Topoisomerase 2 known?

A

DNA Gyrase.

42
Q

What does Helicase do?

A

It melts the hydrogen bonds between base pairs in the double helix.

Open the DNA structure.
Forms the replication fork.

43
Q

What do Helicase monomers form around the leading strand?

A

A doughnut shape hexamer.

44
Q

What does the formation of a doughnut shaped hexamer around the leading strand pull through?

A

New sequences.

Unwinding parental double-stranded ahead of hexamer.

45
Q

How is the lagging strand during DNA replication?

A

Free.

Not bound by Helicase.

46
Q

Where do single-strand DNA-binding (SSB) proteins load onto?

A

On exposed single-strand sections.

47
Q

Why do single-strand DNA-binding proteins load on exposed single-strand sections?

A

To straighten them out.

48
Q

When do single-strand DNA-binding proteins fall off the exposed single-strand sections?

A

When RNA/DNA Polymerase comes along.

49
Q

What does DNA Primase produce at the exposed single-stranded regions?

A

An RNA primer.

50
Q

Why does DNA Primer produce an RNA primer at the exposed single-stranded regions?

A

To allow DNA Polymerase begin synthesis.

51
Q

What does DNA Polymerase do to DNA once it produces RNA primer?

A

It extends primer with new DNA.

52
Q

How is the extension of DA on the leading strand?

A

Continuous.

53
Q

How is the extension of DNA on the lagging strand?

A

Broken into lots of small sections.

54
Q

What does the extension of DNA on the lagging strand produce?

A

Okazaki fragments.

55
Q

What can DNA Polymerase redo?

A

Base pairs mistakes.

56
Q

What does DNA Polymerase manage to do when it can redo base pair mistakes?

A

Reduce level of random mutation.

57
Q

How many exonuclease activities does DNA Polymerase have?

A

2.

58
Q

Which are the 2 exonuclease activities DNA Polymerase have?

A
  1. 3’ –> 5’ exonuclease activity.

2. 5’ –> 3’ exonuclease activity.

59
Q

What does the 3’ –> 5’ exonuclease activity allow DNA Polymerase to do?

A

Remove a mistake.

Replace the wrong nucleotide with the correct one.

60
Q

What does the 5’ –> 3’ exonuclease activity allow DNA Polymerase to do?

A

Remove the next RNA primer when the replication machine has move far enough along the template strand.

61
Q

Where must DNA Polymerase move?

A

Along the template strand in 5’ –> 3’ direction.

62
Q

Why must DNA Polymerase move along the template strand in 5’ –> 3’ direction?

A

To add nucleotides to the growing 3’ -OH end of the new leading strand.

63
Q

In what orientation is the other parental strand?

A

In the opposite orientation.

64
Q

In what direction must a DNA Polymerase synthesizing a new lagging strand for the template (opposite strand) go?

A

In the opposite direction of the template strand.

65
Q

What does DNA Ligase use?

A

ATP.

66
Q

Why does DNA Ligase use ATP?

A

To catalyse the formation of phosphodiester bonds between Okazaki fragments.

67
Q

What does ATP donate?

A

Pyrophosphate.

68
Q

Why does ATP donate pyrophosphate?

A

To form a new 5’-triphosphate tail.

69
Q

Where is the new 5’-triphopshate tail joined?

A

To the adjacent 3’-OH group.

70
Q

Where is DNA Ligase essential?

A

In cloning.

71
Q

What does DNA Ligase allow to happen?

A

2 pieces of DNA –> be linked together.

72
Q

What does looping the DNA around allow?

A

DNA Polymerase synthesizing leading strand and DNA Polymerase synthesizing lagging strand –> movie in same direction.

73
Q

By what is the replication machine lead?

A

By DNA Topoisomerase.

74
Q

What does the replication machine include?

A

DNA Helicase.
RNA Primase.
DNA Ligase.

75
Q

What is different in prokaryotic and eukaryotic enzymes?

A

Different names of enzymes included in the replication machine.

76
Q

Where does DNA replication start?

A

At specific ‘origins’ of replication.

77
Q

Where does DNA replication move?

A

In both directions.

78
Q

What do large chromosomes have?

A

Multiple origins.

79
Q

Why do large chromosomes have multiple origins?

A

To reduce time of replication of DNA before cell division.

80
Q

How many times must each origin fire during DNA synthesis?

A

Only once.

81
Q

How is the fire of origin organised?

A

By timing the synthesis of proteins which control the Origin Recognition. Complex (ORC).

82
Q

Why is the synthesis of the proteins which control the ORC timed?

A

To trigger the S-Phase.

83
Q

What does ORC recruit?

A

Helicase.

84
Q

Why does ORC recruit Helicase?

A

To form the replication fork.

85
Q

What does Phosphorylation of ORC send?

A

A signal that synthesis has begun.

86
Q

What does ORC phosphorylation prevent?

A

Further initiation from the origin site.

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