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Bio 214 > Lecture 9 > Flashcards

Lecture 9 Flashcards

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1
Q

What three things does DNA replication requires?

A
  1. something to copy (parental DNA molecule)
  2. Something to do the copying (enzymes)
  3. Building blocks to make copy (nucleotide triphosphates)
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2
Q

What are the three stages of DNA replication?

A
  1. Initiation- replication begins
  2. Elongation- new strands of DNA are synthesized by DNA polymerase
  3. Termination-replication is terminated
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3
Q

DNA polymerases match existing DNA bases with______ ________ and links them, that is build new DNA strands

A

complementary nucleotides

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4
Q

What are three features of DNA polymerase?

A
  1. add new bases to 3’ end of existing strands
  2. synthesize in 5’ to 3’ direction
  3. require a primer of RNA
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5
Q

______ is used as model system for understanding universal attributes of replication

A

E.coli

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6
Q

What are four characteristics of E.Coli in correlation with Prokaryotic replication?

A

1.singular circular molecule of DNA
2.Replication begins at the origin of replication
3.Proceeds in both directions around the chromosome
4. replicon-DNA controlled by an origin

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7
Q

In prokaryotes, replication is _______ from a unique origin

A

bidirectional

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8
Q

What are the three DNA polymerases in E.coli?

A
  1. DNA polymerase I (Pol I)
  2. DNA polymerase II (Pol II)
  3. DNA polymerase III (Pol III)
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9
Q

What pol is the main replication enzyme?

A

Pol III

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10
Q

What pol is involved in DNA repair processes?

A

Pol II

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11
Q

What Pol acts on lagging strand to remove primers and replace them with DNA?

A

pol I

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12
Q

All three of the polymerase have 3’ to 5’ _____ activity

A

exonuclease

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13
Q

What does exonuclease activity serve as?

A

proofreading

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14
Q

What pol has 5’ to 3’ exonuclease activity when removing RNA primers?

A

Pol I

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15
Q

T or F: some polymerase molecules can remove nucleotides, acting as nucleases

A

True

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16
Q

What does it mean to be endonuclease?

A

cut DNA internally

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17
Q

What does it mean if polymerases are exonucleases?

A

it removes nucleotides from end of DNA

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18
Q

What enzyme unwinds DNA by using energy from ATP?

A

Helicase

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19
Q

What protein coats strands to keep them apart?

A

Single-strand-binding proteins

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20
Q

Unwinding of DNA introduces _____ ____ in the molecule that can lead to additional twisting of the helix

A

torsional strain

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21
Q

What is additional twisting of the helix called?

A

supercoiling

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22
Q

What enzymes prevent supercoiling?

A

topoisomerases

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23
Q

What is the topoisomerase involved in DNA replication that relieves the torsional strain?

A

DNA gyrase

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24
Q

T or F: Replication is semi discontinuous

A

True

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25
Q

T or F: DNA polymerase can only synthesize in the 5’ to 3 direction

A

True

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26
Q

Antiparallel nature of DNA means new DNA strands must be synthesized in ____ directions

A

opposite

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27
Q

What strand is synthesized continuously from an initial primer?

A

Leading strand

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28
Q

What strand is synthesized discontinuously with multiple priming events?

A

lagging strand

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29
Q

DNA fragments on the lagging strand are called _____ _____

A

Okazaki fragments

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30
Q

T or F: synthesis occurs at the replication fork?

A

True

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31
Q

What is the partial opening of helix formed where double stranded DNA is being unwound called?

A

RepliCatIon fork

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32
Q

___ will be removed and replaced with DNA later

A

RNA

33
Q

Does the leading-strand synthesis have multiple priming events?

A

No

34
Q

The leading strand is extended by what Pol?

A

Pol III

35
Q

What is processivity?

A

the ability of a polymerase to stay attached to

36
Q

What subunits form the sliding clamp to keep DNA Pol III attached to DNA?

A

beta

37
Q

T or F: Lagging-strand synthesis does not require additional enzymes

A

False

38
Q

What type of synthesis is the lagging-strand?

A

discontinuous

39
Q

What enzymes are involved in lagging-strand synthesis?

A
  1. DNA Pol III
  2. Primase
    3.DNA Pol I
  3. DNA ligase
40
Q

What does primase do?

A

makes RNA primer for each Okazaki fragment

41
Q

What does DNA Pol I do?

A

removes all RNA primers and replaces with DNA primers

42
Q

What does DNA ligase do?

A

joins Okazaki fragments to form complete strands

43
Q

What occurs at specific site: DNA gyrase unlinks two copies

A

Termination

44
Q

What is a macromolecular assembly of enzymes involved in DNA replication called?

A

replisome

45
Q

What are the main components of a replisome?

A
  1. primosome
  2. complesxof two DNA Pol III
46
Q

What does the primosome consist of?

A

primase, helicase, accessory

47
Q

Why are there two DNA Pol III complexes in the replisome?

A

So there is one for each strand`

48
Q

T or F: Eukaryotic replication and prokaryotic replication have the same complexity

A

False: Eukaryotic replication is more complex

49
Q

Why is eukaryotic replication more complex than prokaryotic replication?

A
  1. larger amount of DNA in multiple chromosomes
    2.Linear structure
50
Q

T or F: Eukaryotic replication uses multiple origins

A

True

51
Q

Why does Eukaryotic replication require new enzymatic activity?

A

Because of dealing with the ends

52
Q

What does it mean if, in replication, there are multiple replicons?

A

There are multiple origins of replications for each chromosome

53
Q

Before _ phase, helicases are loaded onto possible replication origins, but not activated.

A

S

54
Q

During S phase, what is assembled?

A

the replisome

55
Q

What polymerase synthesizes the leading strand?

A

DNA polymerase epsilon

56
Q

What polymerase synthesizes the lagging strand?

A

DNA polymerase delta

57
Q

_______ and eukaryotic replication proteins are evolutionary related

A

Archaeal

58
Q

What enzymes are similar between eukaryotes and archaea but different from those in prokaryotes?

A

DNA polymerase
Replicative helicases
Primases

59
Q

________ chromosomes have specialized ends

A

linear

60
Q

What are Telomeres?

A
  • specialized structures found on the ends of eukaryotic chromosomes
    -composed of repeat sequences
61
Q

What is the role of Telomeres?

A
  1. protect ends of chromosomes from nucleases
  2. maintain the integrity of linear chromosomes
62
Q

The last primer removed from what of the lagging strand cannot be replaced?

A

lagging

63
Q

What is the enzyme that synthesizes the telomere repeat sequences at the ends of stands?

A

Telomerase

64
Q

What does Telomerase use as a template?

A

internal RNA

65
Q

How is telomerase activity regulated?

A

developmentally

66
Q

T or F: DNA damage constantly occurs

A

True

67
Q

What are agents that increase the number of mutations above background level called?

A

mutagens

68
Q

How is the importance of DNA repair indicated?

A

By the multiplicity of repair systems that have been discovered

69
Q

What are the two categories of DNA repair?

A
  1. Specific repair
  2. Nonspecific repair
70
Q

What DNA repair targets a single kind of lesion in DNA and repairs only that damage?

A

specific

71
Q

Which DNA repair uses a single mechanism to repair multiple kinds of lesions in DNA?

A

nonspecific

72
Q

What does the mismatch repair (mmr) do?

A

removes incorrect bases incorporated during DNA replication, by replacing them with the correct base by copying the template strand

73
Q

What strand will be unmethylated for a brief window during which MMR can identify strands?

A

the newly synthesized strand

74
Q

What type of repair mechanism is photorepair?

A

specific

75
Q

What enzyme absorbs light in visible range and uses that energy to cleave thymine dimer?

A

photolyase enzyme

76
Q

What type of repair mechanism is Excision repair?

A

nonspecific

77
Q

What does excision repair do?

A
  1. recognizes the damage
  2. removes the damage region
  3. resynthesis using the information on the undamaged strand as a template
78
Q

T or F: All DNA repair mechanisms are error-free

A

False, some are actually error-prone

Bio 214 (20 decks)

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