Chapter 5 Flashcards

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1
Q

Which enzyme synthesizes RNA primers

A

DNA primase

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2
Q

Relaxes DNA by nicking and then closing one strand of duplex DNA

A

Type I topoisomerase

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3
Q

If E. coli genome requires 20 mins to replicate itself, how can the genome of drosophila be replicated in only 3 mins

A

Drosophila contains more origins of replication than E. coli

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4
Q

What kind of nucleotide has a two-ring structure with an amine functional group

A

Purine

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5
Q

The duplication of genetic information carried in chemical form as DNA

A

DNA replication

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6
Q

Permanent change in the DNA

A

Mutation

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7
Q

The rate at which observable change occurs in DNA sequences

A

Mutation rate

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8
Q

The mechanism the cell uses to copy the nucleotide sequence

A

DNA templating

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9
Q

First nudeotide-polymerizing enzyme

A

DNA polymerase

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10
Q

Each nucleotide added to a growing DNA strand comes from

A

Nucleoside (a sugar and a base) triphosphate (3 phosphate groups)

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11
Q

What happen when nucleosides pair and the 2 phosphate groups are released

A

Provides energy for phosphodiester bond

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12
Q
A

Semiconservative replication

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13
Q
A

Conservative replication

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14
Q
A

Dispersive replication

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15
Q

A localized region of replication that moves progressively along the parental DNA double helix

A

Replication fork

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16
Q

Origin of replication takes place where which base pairs are predominant

A

A and T

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17
Q

Binds to double helix and breaks hydrogen bonds

A

DNA helicase

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18
Q

Changes DNA topology by breaking and rejoining double - stranded DNA

A

Type II topoisomerase

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19
Q

Polymerized only in the 3’ to 5’ chain direction

A

Okazaki fragments

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20
Q

Daughter strand that is synthesized continuously

A

Leading strand

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21
Q

Daughter strand that is synthesized discontinuously

A

Lagging strand

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22
Q

The synthesis of each Okazaki fragment ends when

A

DNA polymerase runs into the RNA primer attached the 5’ end of previous daughter fragment

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23
Q

Bind tightly and cooperatively to exposed single-stranded DNA stabilizing the unwound, single-stranded conformation

A

Single strand dna-binding proteins (ssb)

24
Q

After the polymerase “double-checks” its base pairing the next error-correcting reaction is

A

Exonucleolytic proofreading

25
Q

Clips off any unpaired residues at the primer terminus

A

Proofreading exonuclease

26
Q

Why do RNA polymerase enzymes not need an efficient exonucleolytic proofreading mechanism

A
  • Errors in RNA are not passed on

- Defective RNA molecule has no long term significance

27
Q

The Initiation of DNA replication is highly regulated. Once DNA helicase is loaded, it

A

Begins to unwind DNA exposing DNA for primase to synthesize the RNA primer

28
Q

An origin of replication experiences what caused by a delay in the methylation of “A’ nucleotides

A

Refractory period

29
Q

Initiation is blocked until

A

“As” are methylated

30
Q

Human cells growing in culture are labeled for a short time with

A

^3H-thymidine (radioisotope of hydrogen)

31
Q

Development of the emulsion reveals the pattern of labeled DNA through

A

Autoradiography

32
Q

The rate and the direction of replication-fork movement can be determined by

A

Autoradiography

33
Q

Replication origins tend to be activated in clusters called

A

Replication units

34
Q

DNA replication in most eucaryotic cells occur during

A

The S phase

35
Q

Are replication origins activated simultaneously?

A

No

36
Q

How can replication fork initiation and fork movement accurately monitored?

A

DNA microarrays

37
Q

Particularly condensed state of chromatin

A

Heterochromatin

38
Q

Less condensed chromatin

A

Euchromatin

39
Q

Tends to be replicated very late in phase

A

Heterochromatin

40
Q

Regions of the genome whose chromatin is least condensed are replicated

A

First

41
Q

Each DNA sequence that can serve as an origin of replication contain:

A
  • A binding size for ORC (origin recognition complex)
  • A stretch of DNA rich in As and Ts
  • At least one binding site for proteins that help attract ORC
42
Q

How is replication regulated to ensure all the DNA is copied only once

A

ORC complex

43
Q

2 DNA helicase loadings proteins

A

cdc6 and cdt1

44
Q

Passage of a cell from G1 to S phase is triggered by the activation of

A

Protein kinases

45
Q

Contain tandem repeats of a short sequence (GGGGTT)

A

Telomeres

46
Q

Replaces tandem repeats each time a cell divides and recognizes the tip of an existing repeat sequence

A

Telomerase

47
Q

Processes that correct spontaneous DNA changes

A

DNA repair

48
Q

DNA changes are caused by

A
  • Heat
  • metabolic accidents
  • radiation
  • exposure to environmental substances
49
Q

Extreme sensitivity to UV radiation

A

Xeroderma pigmentosum

50
Q

Can release guanine and adenine from DNA

A

Depurination

51
Q

Converts DNA base to an altered base

A

Deamination

52
Q

Covalent linkage between two adjacent pyrimidine bases

A

Thymine dimers

53
Q

Recognizes wrong base, removes, and inserts correct nucleotide

A

Base excision repair

54
Q

Large mutation/abnormal helix shape, remove multiple nucleotides, synthesizes nucleotides with DNA polymerase

A

Nucleotide excision repair

55
Q

Both strands of double helix are broken, broken ends are brought together and rejoined

A

Nonhomologous end joining

56
Q

Both strands are broken, uses sister chromatids to repair

A

Homologous recombination