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Biochemistry > Replication > Flashcards

Replication Flashcards

(96 cards)

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1
Q

What is the genetic material in cells

A

DNA

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2
Q

What happens to genetic material during cell division

A

It is identically passed to daughter cells

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3
Q

What is DNA replication

A

Process of copying DNA to form identical molecules

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4
Q

Why is high fidelity in replication important

A

Essential for species survival

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5
Q

What type of replication occurs in prokaryotes

A

Semiconservative

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6
Q

Who provided experimental evidence for semiconservative replication

A

Meselson and Stahl (1958)

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7
Q

What is conserved in semiconservative replication

A

One strand of parental DNA

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8
Q

What is the initiation site of DNA synthesis called

A

Origin of replication

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9
Q

How many origins of replication are in prokaryotes

A

One

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10
Q

How many origins of replication are in eukaryotes

A

Multiple

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11
Q

What base pair sequence is common at origin sites

A

Short sequence of A-T base pairs

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12
Q

What protein binds to origin of replication in prokaryotes

A

dna A

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13
Q

What happens when dna A binds to origin

A

Double-stranded DNA separates

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14
Q

What forms when DNA strands separate at replication site

A

Replication bubble

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15
Q

Why are multiple replication bubbles important in eukaryotes

A

For rapid replication

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16
Q

What is required to initiate DNA synthesis

A

RNA primer

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17
Q

What enzyme synthesizes RNA primers

A

Primase

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18
Q

What complex synthesizes RNA primers

A

Primosome

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19
Q

Where is constant RNA primer synthesis needed

A

Lagging strand

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20
Q

How many RNA primers are usually on leading strand

A

One

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21
Q

What is the direction of DNA synthesis

A

5’ to 3’

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22
Q

What is the leading strand

A

Continuously synthesized DNA strand

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23
Q

What is the lagging strand

A

Discontinuously synthesized DNA strand

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24
Q

What are short DNA pieces on lagging strand called

A

Okazaki fragments

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25
What is meant by bidirectional DNA synthesis
Occurs in both directions from origin
26
What is the replication fork
Region where parent DNA strands separate for synthesis
27
Which enzymes open up the DNA helix
DNA helicases
28
What is the energy source for helicase activity
ATP
29
What proteins stabilize separated DNA strands
Single-stranded binding proteins
30
What do SSB proteins prevent
Degradation of single-stranded DNA and keep the two strands seperate
31
Which enzyme catalyzes main DNA synthesis
DNA polymerase III
32
What is required for DNA polymerase III activity
All four dNTPs
33
What is released with each nucleotide addition
Pyrophosphate (PPi)
34
What determines the new DNA base sequence
Template DNA strand
35
What is the polarity problem in DNA synthesis
No polymerase can add to 5' end
36
How is polarity problem solved
Lagging strand made as Okazaki fragments
37
What joins Okazaki fragments
DNA polymerase I and DNA ligase
38
What proofreading activity does DNA polymerase III have
Removes mismatched nucleotides
39
What replaces RNA primer in prokaryotes
DNA synthesized by DNA polymerase I
40
What seals nick between DNA fragments
DNA ligase
41
What is the energy source for ligase activity
ATP (converted to AMP + PPi)
42
Which enzyme participates in DNA repair in prokaryotes
DNA polymerase II
43
What causes supercoiling during replication
Unwinding of DNA helix
44
What enzymes resolve DNA supercoils
DNA topoisomerases
45
What does Type I topoisomerase do
Cuts and reseals single DNA strand
46
What does Type II topoisomerase (gyrase) do
Cuts and reseals both DNA strands
47
What characterizes eukaryotic replication
Multiple origins and 5 DNA polymerases
48
What does DNA polymerase alpha do
Synthesizes RNA primer for both strands
49
What is the role of DNA polymerase beta
DNA repair
50
What is the role of DNA polymerase gamma
Replicates mitochondrial DNA
51
What does DNA polymerase theta do
Replicates leading strand and proofreads
52
What does DNA polymerase theta do
Replicates lagging and leading strand and proofreads
53
What is PCNA
Sliding clamp for DNA polymerase (proliferating cell nuclear antigen)
54
What is the role of replication factor C (RFC)
Loads PCNA onto DNA
55
What binds to exposed DNA in eukaryotes
Replication protein A (RPA)
56
What synthesizes Okazaki fragment primers in eukaryotes
Primase in pol alpha-primase complex
57
What removes RNA primers in eukaryotes
RNase H and FEN1
58
What fills gaps left by primer removal
DNA polymerase theta
59
What seals nicks in eukaryotic DNA
DNA ligase
60
What proteins bind DNA to form nucleosomes
Histones
61
How are histones distributed after replication
Old histones to one strand, new to the other
62
Which enzyme is targeted by ciprofloxacin
Bacterial gyrase
63
What phase of cell cycle involves DNA replication
S-phase
64
How long does S-phase DNA synthesis take
8-10 hours
65
What marks DNA to inhibit re-replication
Methylation
66
What proteins regulate cell cycle phases
Cyclins
67
What enzymes do cyclins activate
Cyclin-dependent kinases (CDKs)
68
What happens at cell cycle checkpoints
Damage is checked and corrected
69
What occurs if DNA damage is unrepairable
Apoptosis
70
Which cancer drugs inhibit nucleotide synthesis
Methotrexate, 5-fluorouracil
71
What challenge exists in replicating linear eukaryotic chromosomes
Lagging strand cannot be fully synthesized
72
Why can't the lagging strand be fully replicated
RNA primer removal leaves a gap
73
What happens to daughter chromosomes due to incomplete lagging strand replication
DNA molecules become shortened
74
When does chromosome shortening become significant
After several replication cycles
75
What is the consequence of losing essential genes from chromosomes
Cell death
76
What prevents loss of DNA at chromosome ends during replication
Telomeres
77
What are telomeres
Special structures at chromosome ends preventing DNA loss
78
What additional function do telomeres have
Prevent chromosome fusion
79
What type of sequence are telomeres made of
Repeated six-nucleotide sequences
80
What is the telomere repeat sequence in humans
TTAGGG
81
What is the approximate length of human telomeres
Up to 1500 bp
82
What enzyme maintains telomeres
Telomerase
83
What is another name for telomerase
Telomere terminal transferase
84
What is unique about telomerase composition
Contains both protein and RNA
85
How long is the RNA component of human telomerase
450 nucleotides
86
What is the 5�-terminal RNA sequence of human telomerase
5'-CUAACCCUAAC-3'
87
What sequence is complementary to the telomere repeat
5'-TTAGGG-3'
88
What role does telomerase RNA play in telomere extension
Acts as template for DNA synthesis
89
What happens after initial telomerase extension
Telomerase translocates and extends further
90
Which enzymes finalize telomere DNA synthesis
DNA polymerase and primase complex
91
Do telomeres encode proteins
No
92
Is shortening of telomeres always harmful
No, some shortening is tolerable
93
When is telomerase highly active
In early embryo, reproductive, and stem cells
94
What role do stem cells have
Continuously divide to maintain tissues and organs
95
What is the proposed link between telomere shortening and senescence
Shortening may trigger cell death
96
What makes telomerase a cancer therapy target
Inactivation induces senescence and stops cancer cell proliferation

Biochemistry (12 decks)

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