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MBG 2040 > Replication > Flashcards

Replication Flashcards

(61 cards)

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1
Q

why is dan replication important

A
  • ensures that an exact copy of a species lives on

- essential for the continuation of life

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2
Q

which dna bases have three bonds between them

A

G and C are complementary and share three H bonds between them

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3
Q

which DNA bases have two bonds between them

A

A and T are complementary and share two H bonds between them

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4
Q

how many base pairs are in one turn in DNA

A

10 base pairs per turn

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5
Q

what is the distance per stacked base

A

0.34nm

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6
Q

how long is each helical turn

A

3.4nm

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7
Q

how conservative id dna replication

A

dna replication is semi-conservative

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8
Q

what are the four steps to semi-conservative dna replication

A
  • parental dna
  • separation of parental strands
  • synthesis of new complementary strands
  • two identical daughter dna molecules
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9
Q

describe the dna strands after one round of dna replication

A

after one round of dna replication, each dna contains 1 parental and 1 newly synthesized strand

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10
Q

describe conservative dna

A

will always have one daughter dna identical to the original dna

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11
Q

describe dispersive replication

A

amount of original dna present decreases as more replication occurs (mixed strands of original +new)

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12
Q

describe semi-conservative dna replication

A

some new strands will have original strand dna incorporated, but some wont

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13
Q

what are the three modes of dna replication

A

1) theta replication
2) rolling circle replication
3) linear chromosome replication

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14
Q

what type of replication occurs in most circular dna

A

theta replication

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15
Q

what are the steps of theta replication

A

1) double strand dna unwinds at the replication origin
2) replication bubble forms
3) newly formed dna outlines the replication bubble as it spreads around the entire circle
4) two circular dna molecules are formed

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16
Q

is theta replication uni or bi directional

A

bidirectional

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17
Q

describe rolling circle replication

A

specialized form of replication that occurs in the F factor and some viruses

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18
Q

what is the form of replication within the F factor and some viruses

A

rolling circle replication

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19
Q

describe the steps in rolling circle replication

A
  • replication is initiated by a break in one of the nucleotide strands
  • dna synthesis begins at the 3’ end of the broken strand (the inner strand is uses as a template
  • cleavage releases a single-stranded linear dna and a double-stranded circular dna
  • the linear dna may circularize and serve as a template for synthesis of a complementary strand
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20
Q

describe linear chromosome replication

A
  • each chromosome contains numerous origins
  • at each origin, the dna unwinds (producing a replication bubble)
  • dna synthesis takes place on both strands at each end of the bubble
  • eventually, the forks of adjacent bubbles run into each other and the segments of dna fuse
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21
Q

what does an RNA primer do

A

provides the 3’ OH end to initiate dna synthesis by DNA polymerase

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22
Q

what direction is dna synthesized in

A

5’ to 3’

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23
Q

what type of bond is formed between nucleotides

A

phosphodiester bond

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24
Q

what does chain cleavage result in

A

chain cleavage can result in the alpha phosphate group attached to the 5’ carbon or the 3’ carbon of the deoxyribose sugar

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25
dna synthesis is _____ on the leading strand and _____ on the lagging strand
dna synthesis is continuous on the leading strand and discontinuous on the lagging strand
26
what are Okazaki fragments
discontinuous fragments of dna produced by discontinuous synthesis on the lagging strand
27
what is oriC
the origin of replication
28
describe what happens during the priming of oriC
- primers bind to oriC, causing a short length of dna to unwind - this unwinding allows helicase and other single-stranded-binding proteins to attach to the single-stranded dna
29
what happens when helicase binds to single-stranded prokaryotic dna during the priming of oriC
-helicase unwinds the dna in the 5' to 3' direction (travels on the lagging strand ahead of the replication machinery) -breaks the hydrogen bonds between the bases, and moves the replication fork forward
30
what does dna gyrase do
during the priming of oriC, dna gyrase releases strain ahead of the replication fork as helicase unwinds the dnA
31
how are positive supercoils formed
helicase-induced unwinding of the double helical dna causes the dna ahead to be overwound
32
in bacteria, what releases the positive supercoils
in bacteria, a specialized dna topoisomerase 2 (dna gyrase) nicks the dna and releases the supercoils
33
why are supercoils bad
they stop replication
34
what does dna primase do
dna primase synthesizes a short RNA primer that provides the 3'OH end for DNA polymerase to begin dna synthesis
35
where is the primer needed for strand synthesis in prokaryotes on the leading strand
on the leading strand (where replication is continuous), a primer is required only at the 5' end of the newly synthesized strand
36
where its the primer needed on the lagging strand in prokaryotic dna
on the lagging strand (where replication is discontinuous), a new primer must be generated at the beginning of each Okazaki fragment
37
what dna polymerases are for chromosomal dna replication
DNA polymerase 1 and 3 have functions that have to do with chromosomal dna replication
38
what dna polymerases are for dna repair
DNA polymerase 2, 4, 5 have functions that have to do with dna repair
39
main function of DNA polymerase 1
aids in the removal of rna primers
40
describe the direction of polymerase and exonuclease activity for dna pol 1
DNA polymerase 1 has 5' to 3' polymerase and exonuclease activity
41
what is the direction for proofreading exonuclease activity for DNA polymerase 1
for proofreading (cutting out mistakes), DNA polymerase 1 has 3' to 5' exonuclease activity
42
is DNA polymerase 1 processive
DNA polymerase 1 is not highly processive- it has short tract synthesis
43
what is the function of polymerase 3
DNA polymerase 3 is the main replication polymerase
44
what direction does DNA polymerase 3 carry out its polymerase activity
DNA polymerase 3 has 5' to 3' polymerase activity
45
what direction does DNA polymerase 3 carry out its exonuclease activity
DNA polymerase 3 has 3' to 5' exonuclease activity
46
is DNA polymerase 3 processive
DNA polymerase 3 is highly processive
47
what is a beta sliding clamp and what does it do
beta sliding clamp is a ring-shaped polypeptide that encircles the dna and interacts with DNA polymerase 3 to enhance processive dna synthesis
48
what happens when dna synthesis by polymerase 3 reached the 5' end of a lagging strand
when dna synthesis by polymerase 3 reaches the 5', polymerase 3 is swapped for polymerase 1.
49
what happens after polymerase 3 is swapped for polymerase 1 on the lagging strand
DNA polymerase 1 (which has 5' to 3' exonuclease activity and 5' to 3' polymerase activity) removes the rna primer and re-synthesizes a short tract of dna
50
what type of bond does dna ligase make between the 5'phosphate and the 3'oh group of the lagging strand
dna ligase makes a phosphodiester bond between the 5'phosphate and the 3'OH group
51
what are the four steps of polymerases on the lagging strand
1. dna nucleotides are added to the primer by dna polymerase 3 2. DNA polymerase 1 replaces the rna nucleotides of the primer with dna nucleotides 3. after the last nucleotide of the rna primer has been replaced, a nick remains in the sugar-phosphate backbone of the strand 4. dna ligase seals this nick with a phosphodiester bond between 5'P group of the initial nucleotide added by polymerase 3 and the 3'OH group of the final nucleotide added by polymerase 1
52
what does elongation during replication involve
involves coordinated activity of DNA polymerase 3 on the lagging strand in order for replication to keep up with that on the leading strand
53
what does elongation during replicated require in terms of Okazaki strands
elongation during replication required DNA polymerase 3 to complete one Okazaki fragment, then move and initiate dna synthesis of a new Okazaki strand
54
while DNA polymerase 3 is completing new Okazaki fragments, what is polymerase 1 doing
DNA polymerase exchanged places with DNA polymerase 3 to remove rna primers
55
why must dna form a loop during elongation
dna must form a loop so that both strands can replicate simultaneously
56
in eukaryotic organisms, when does dna replication occur
dna replication only occurs during s phase
57
what is the function of epsilon polymerase in eukaryotic replication
performs leading strand replication
58
what is the function of delta polymerase in eukaryotic replication
performs lagging strand replication
59
what is the function of alpha polymerase in eukaryotic replication
has primase activity
60
describe nucleosomes in eukaryotes
nucleosomes need to be removed from parental dna and properly re-assembled on newly synthesized dna
61
what are telomeres and what type of organisms are they found in
found in eukaryotes, telomeres are the ends of chromosomes (they shorten at each round of replication)

MBG 2040 (2 decks)

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