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Bio 214 > Lecture 9 > Flashcards

Lecture 9 Flashcards

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
T or F: DNA polymerase can only synthesize in the 5' to 3 direction
True
26
Antiparallel nature of DNA means new DNA strands must be synthesized in ____ directions
opposite
27
What strand is synthesized continuously from an initial primer?
Leading strand
28
What strand is synthesized discontinuously with multiple priming events?
lagging strand
29
DNA fragments on the lagging strand are called _____ _____
Okazaki fragments
30
T or F: synthesis occurs at the replication fork?
True
31
What is the partial opening of helix formed where double stranded DNA is being unwound called?
RepliCatIon fork
32
___ will be removed and replaced with DNA later
RNA
33
Does the leading-strand synthesis have multiple priming events?
No
34
The leading strand is extended by what Pol?
Pol III
35
What is processivity?
the ability of a polymerase to stay attached to
36
What subunits form the sliding clamp to keep DNA Pol III attached to DNA?
beta
37
T or F: Lagging-strand synthesis does not require additional enzymes
False
38
What type of synthesis is the lagging-strand?
discontinuous
39
What enzymes are involved in lagging-strand synthesis?
1. DNA Pol III 2. Primase 3.DNA Pol I 4. DNA ligase
40
What does primase do?
makes RNA primer for each Okazaki fragment
41
What does DNA Pol I do?
removes all RNA primers and replaces with DNA primers
42
What does DNA ligase do?
joins Okazaki fragments to form complete strands
43
What occurs at specific site: DNA gyrase unlinks two copies
Termination
44
What is a macromolecular assembly of enzymes involved in DNA replication called?
replisome
45
What are the main components of a replisome?
1. primosome 2. complesxof two DNA Pol III
46
What does the primosome consist of?
primase, helicase, accessory
47
Why are there two DNA Pol III complexes in the replisome?
So there is one for each strand`
48
T or F: Eukaryotic replication and prokaryotic replication have the same complexity
False: Eukaryotic replication is more complex
49
Why is eukaryotic replication more complex than prokaryotic replication?
1. larger amount of DNA in multiple chromosomes 2.Linear structure
50
T or F: Eukaryotic replication uses multiple origins
True
51
Why does Eukaryotic replication require new enzymatic activity?
Because of dealing with the ends
52
What does it mean if, in replication, there are multiple replicons?
There are multiple origins of replications for each chromosome
53
Before _ phase, helicases are loaded onto possible replication origins, but not activated.
S
54
During S phase, what is assembled?
the replisome
55
What polymerase synthesizes the leading strand?
DNA polymerase epsilon
56
What polymerase synthesizes the lagging strand?
DNA polymerase delta
57
_______ and eukaryotic replication proteins are evolutionary related
Archaeal
58
What enzymes are similar between eukaryotes and archaea but different from those in prokaryotes?
DNA polymerase Replicative helicases Primases
59
________ chromosomes have specialized ends
linear
60
What are Telomeres?
- specialized structures found on the ends of eukaryotic chromosomes -composed of repeat sequences
61
What is the role of Telomeres?
1. protect ends of chromosomes from nucleases 2. maintain the integrity of linear chromosomes
62
The last primer removed from what of the lagging strand cannot be replaced?
lagging
63
What is the enzyme that synthesizes the telomere repeat sequences at the ends of stands?
Telomerase
64
What does Telomerase use as a template?
internal RNA
65
How is telomerase activity regulated?
developmentally
66
T or F: DNA damage constantly occurs
True
67
What are agents that increase the number of mutations above background level called?
mutagens
68
How is the importance of DNA repair indicated?
By the multiplicity of repair systems that have been discovered
69
What are the two categories of DNA repair?
1. Specific repair 2. Nonspecific repair
70
What DNA repair targets a single kind of lesion in DNA and repairs only that damage?
specific
71
Which DNA repair uses a single mechanism to repair multiple kinds of lesions in DNA?
nonspecific
72
What does the mismatch repair (mmr) do?
removes incorrect bases incorporated during DNA replication, by replacing them with the correct base by copying the template strand
73
What strand will be unmethylated for a brief window during which MMR can identify strands?
the newly synthesized strand
74
What type of repair mechanism is photorepair?
specific
75
What enzyme absorbs light in visible range and uses that energy to cleave thymine dimer?
photolyase enzyme
76
What type of repair mechanism is Excision repair?
nonspecific
77
What does excision repair do?
1. recognizes the damage 2. removes the damage region 3. resynthesis using the information on the undamaged strand as a template
78
T or F: All DNA repair mechanisms are error-free
False, some are actually error-prone

Bio 214 (23 decks)

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