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DNA replication Flashcards

1
Q

replication

A

information must be able to be copied during cell division

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2
Q

what does replication need

A

a template for an accurate copy

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3
Q

central dogma

A

replication –> transcription –> translation –> expression

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4
Q

three models of how DNA was replicated

A
  1. conservative
  2. semiconservative
  3. dispersive
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5
Q

conservative replication

A

two strands remain together or pair again after replication

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6
Q

semiconservative replication

A

after replication, each product contains one parent strand and a nascent strand

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7
Q

dispersive replication

A

parental strands are cleaved into dsDNA segments and reassembled with interspersed nascent strands

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8
Q

Meselson-Stahl experiment generation 0

A

15N was incorporated into every molecule that contains N –> N 15 is heavier than naturally occurring N
- 15N/15N (all the same)

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9
Q

Meselson-Stahl experiment generation 1

A

15N labeled E coli added to 14N, cells replicate once in 14N
- 15N/14N
- half heavy N and half lighter N

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10
Q

Meselson-Stahl experiment generation 2

A

cells replicate one more time in 14N from generation 1 (15N/14N)
- 14N/14N
- 15N/15N

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11
Q

Meselson-Stahl experiment generation 3

A

cells replicate a third time from generation 2 with 14N
- more of 14N/14N
- less of 15N/14N

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12
Q

Meselson-Stahl experiment is an example of

A

semi-conserved replication

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13
Q

conditions for DNA replication

A
  1. G1
  2. S
  3. G2
  4. M
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14
Q

G1

A
  • interphase
  • before chromosome duplication
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15
Q

S

A
  • DNA synthesis
  • DNA replication
  • chromosome duplication
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16
Q

G2

A
  • interphase
  • before cell division
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17
Q

M

A

cell division

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18
Q

3 phases of DNA replication

A
  1. initiation
  2. elongation
  3. termination
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19
Q
  1. initiation in prokaryotes/bacteria
A
  • single point of origin
  • 245 base pairs (AT rich repeat region)
  • DNA initiator binds to repeat region which INITIATES REPLICATION
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20
Q
  1. initiation in eukaryotes
A
  • many origin of replication per chromosome
  • required pre-replication complex
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21
Q

pre-replication complex

A

controls the timing of DNA replication by marking origins at the start of each G1 phase of the cell cycle

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22
Q
  1. Elongation
A
  • occurs in all organism
  • DNA polymerase catalyzes polymerization
  • new DNA strand always grows 5’ - 3’ !!!!!!
  • bidirectional
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23
Q

polymerization

A

joining of new nucleotides to the proceeding nucleotide using a phosphodiester bond formation

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24
Q

bidirectional

A

proceeds on leading and lagging strands at the same time

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25
elongation: 5' - 3'
5' carbon is added to the 3' carbon of the growing chain - cleaves off 2 phosphates: requires energy - is catalyzed by DNA polymerase
26
3. Termination - circular bacteria
- prokaryotes - DNA synthesis reaches starting point and polymerase falls off the template
27
3. Termination - linear eukaryotes
more complicated** - DNA pol can not synthesize new strands at the tips of 5' single strand ends - 5' ss ends resemble ds break
28
Enzymes for DNA replication
- helicase - single stranded binding proteins - primase (polymerase - alpha) - polymerase III (pol delta and - okazaki fragments - polymerase I - RNA primers - DNA gyrase - DNA ligase
29
helicase
- binds at replication origin - denatures dsDNA by breaking H bonds between bases
30
single stranded binding proteins
- bind to ssDNA to prevent reannealing - displaced by polymerase as it moves along the strand
31
primase (polymerase alpha in eukaryotes)
- associates with DNA replication origin - RNA polymerase that synthesizes a short RNA primer - can only add nucleotides to pre-existing strand - primer base pairs with template following complementary base pairing
32
DNA polymerase III
- adds nucleotides to the 3' end of existing strands only - synthesizes from the RNA primer for both the leading and lagging strands simultaneously - **adds dNTPs to end of 3' growing strand ** - moves 5' - 3'
33
what does DNA polymerase III use
holoenzyme and sliding clamp
34
holoenzyme
subunits and cofactors combined that allows catalytic activity of the enzyme
35
sliding clamp
holds polymerase on DNA template
36
components of the lagging strand
- Okazaki fragments - polymerase I - DNA ligase - DNA gyrase
37
Okazaki fragments
- short lagging strand fragments - requires RNA primer - 5' - 3' direction - helps lagging strand become synthesized
38
Okazaki fragments - prokaryotes/bacteria
1200 nucleotides - achieved through supercoiling - fewer proteins are present
39
Okazaki fragments - eukaryotes
100-300 nucleotides - highly complex - involves histones - fragments are encountered more here - pol delta does not have 5' exonuclease activity so it can not remove the RNA primer - additional enzymes are required to displace and remove the RNA primers
40
polymerase I
- replaces RNA primers with dNTPs using polymerase activity - digests primer ahead of it using its 5' - 3' exonuclease activity
41
DNA ligase
seals nicks between adjacent fragments
42
DNA gyrase
topoisomerase II relaxes supercoiling
43
nucleosomes and DNA replication
- histones spaced throughout eukaryotic DNA - blocks access of DNA polymerase to replication origins - at replication fork, the histones are disassembled - nucleosomes (DNA and histone) immediately reform after DNA is synthesized: DNA subunits
44
DNA subunits
they are reused and new proteins are synthesized while DNA is synthesized
45
what does DNA subunits ensure
that there are enough histones available to repack DNA
46
2 DNA polymerase
Pol I (discovered first) Pol III (holoenzyme which is essential for replication)
47
processivity
how many base pairs polymerase can add before it falls off
48
what increases processivity
sliding clamp
49
fidelity
accuracy in adding base pairs - how many times does polymerase incorporate the wrong base
50
what increases fidelity
proofreading activity
51
exonuclease activity
removal of nucleotides during proofreading or replacing RNA primers
52
proofreading
remove incorrect 3' base, add correct base and continue synthesizing - both pol I and pol III
53
5' - 3' polymerase activity
DNA pol I and pol III - new strand grows 5' - 3'
54
3' - 5' polymerase activity
NONE - polymerization does not occur 3' - 5'
55
5' - 3' exonuclease activity
DNA pol I - removes the RNA primers form 5' - 3'
56
3' - 5' exonuclease activity
DNA pol I and pol III - both perform 3' - 5' proofreading
57
telomerase
adds addition repeats to ending sequence due to the end of chromatin containing repetitive DNA (G-rich)
58
telomerase uses
holoenzyme and ribonucleoprotein
59
ribonucleoprotein
contains RNA (TERC) and protein (TERT)
60
reverse transcriptive activity
synthesizes DNA from RNA template
61
TERC
ncRNA
62
in telomerase RNA provides
a guide to attach enzymes and a template to initiate DNA replication
63
TERT
telomerase reverse transcriptiate
64
stabilizing proteins
dyskerin, GAR, NHP2, NOP10
65
shelterins
protein complex that stabilizes the ends of chromosomes by forming a loop
66
what do shelterins prevent
DNA repair mechanisms from attempting to stick chromosomes together
67

Genetics (4 decks)

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