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DNA Replication Flashcards

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1
Q

What were people uncertain genetic material was in the early 20th century?

A

Carbohydrates
protein
lipid
something else

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2
Q

Recognition that _ was genetic material was a key insight

A

DNA

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3
Q

What did DNAs structure immediately suggest?

A

DNA could serve as a blueprint and that blue print could be passed down through generations

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4
Q

Where are genes carried?

A

chromosomes

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5
Q

What are chromosomes comprised of?

A

DNA and proteins

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6
Q

Experiements suggested that the _ component of chromosomes is the genetic material

A

DNA

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7
Q

What was Fredrick Griffith’s experiement with?

A

Mice and streptococcus pneumoniae

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8
Q

What cells killed inoculated mice?

A

Smooth cells
S-strain

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9
Q

What cells did not kill inoculated mice

A

Rough cells
R-strain

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10
Q

How do you eliminate the virulence in the s-strain

A

with heat

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11
Q

What happens to a mouse with live R-strain cells and heat-killed S-strain? and what was recovered?

A

Mouse dies
Live S-strain was recovered

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12
Q

What does recovering live S-strains from dead mice tell us?

A

Cell debris from dead S-cells had converted R cells into S-cells

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13
Q

Avery-Mcarty-Mcleod

What material in the cell debris was responsible for the transformation of the S cell DNA into the live R cells?
How do we know?

A

DNA
The mouse did not live until the DNA debris was destroyed

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14
Q

What was the first evidence that DNA was genetic material?
(From Griffith, Avery-mccarty-mcleod experiment)

A

The mouse with live R-cells and dead S-cells did not live until the S-cell DNA debris was destroyed

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15
Q

What was the Hershey-Chase experiement?

A

Phages with radiolabeled protein and phages with radiolabeled DNA were used to infect hosts. The host cells were then processed to see if the radiolabel was within cells or outside of cells. Radioactive DNA was recovered in bacteria due to the radiolabeled DNA.

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16
Q

What was recovered in the Hershey-Chase experiment?

A

Bacteria with radioactive DNA

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17
Q

Structural features of DNA must allow for _ _

A

Faithful replication

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18
Q

Genetic material must have _ _

A

informational content

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19
Q

Genetic material _ be able to change on rare occaision

A

must

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20
Q

What 3 pieces of information about DNA
were crucial in determining its structure

A

The chemical composition of DNA
Chargaff’s rule
X-ray crystallography

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21
Q

What are the 3 components of DNA?

A

Tri-hosphate
a deoxyribose sugar
A nitrogenous base

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22
Q

What are the 4 nitrogenous bases of DNA

A

Purines: adenine and guanine
Pyrimidines: cytosine and thymine

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23
Q

Purine structure?

A

double ring

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24
Q

Pyrimidine structure?

A

single ring

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25
What is chargaffs rule?
T=A, C=G but A+T does not necesarily = C+G
26
Who conducted x-ray crystallography of DNA
Rosalind Franklin and Maurice Wilkins
27
What did x-ray crystallography suggest?
DNA is long, skinny, helical and comprised of two similar parts
28
What happened in approx 1953?
James watson and francis crick inferred that DNA is a double helix
29
Watson and Crick "_ must always pair with _ because..."
Purine must always pair with a pyrimidine because it is most consistent with xray data
30
What are DNA's complementary base pairs?
A-T C-G
31
What holds the strands of DNA together
Hydrogen bonding between the nucleotides
32
How many Hydrogen bonds does A-T have? C-G?
AT-2 CG-3
33
Where do base pairs stack in DNA?
In the center of DNA as planar structures
34
Do major and minor grooves impact its function?
yes Alternating minor and major
35
Meselson-Stahl experiment found that DNA replication is _
Semi-conservative
36
What does semi-conservative replication mean?
1 old strand and 1 new strand
37
When do you see the replication fork?
Second round of replication
38
Replicating DNA is mixed between _ and _ states
unwound and overwound states
39
_ _ removes twists and supercoils to make replication possible
DNA gyrase
40
_ unwinds double helix at the replication fork and SSB binds
Helicase
41
_ _ cuts DNA strands and rotates them to prevent supercoiling
DNA gyrase
42
What rejoins the strands
DNA gyrase
43
_ help relive tension in DNA
Topoisomerases (gyrase)
44
What do topoisomerases do?
Break the phosphodiester bonds between nucleotides and then reseal these breaks
45
# E.coli Initiation of replication begins at the ___
Origin (oriC)
46
# E.coli DnaA binds to _ _ which are specific _ _ _
DnaA binds to DnaA boxes, which are specific, short DNA sequences
47
# E.coli What is adjacent to DnaA boxes?
AT-rich sequences that melt easily which opens up the DNA
48
# E.coli What do additional DnaA molecules do once DNA is opened up a bit?
additional DnaA molcules bind to the DNA less specifically
49
# E.coli Opening up of the DNA leads to the recruitment and loading of _
Leads to the recruitment and loading of DnaB (helicase)
50
# E.coli Once bound _ (DnaB) further _ _ _
Once bound helicase (DnaB) further opens the DNA
51
# E.coli After helicase further opens up DNA this leads to the recruitment of the _
replisome
52
# E.coli What does the replisome do?
It allows for DNA polymerase to come in and synthesize a complementary DNA strand
53
# E.coli What is DNA polymerase?
The enzyme that synthesizes a complementary strand of DNA
54
# E.coli Who isolated DNA polymerase from E.coli and demonstrated its function in vitro
Arthur Kornberg
55
# E.coli How many DNA polymerases does E.coli have?
5
56
# E.coli DNA pol I catalyzes chain growth _ - _ end
5' to 3'
57
# E.coli DNA pol I additional 3' to 5' exonuclease activity
Removes mismatched bases
58
# E.coli DNA pol I additional 5' to 3' exonuclease activity
Degrades single strands of DNA or RNA
59
# E.coli Which DNA pol does most of the work in replication in E.coli ?
DNA pol III
60
# E.coli What are the two types of strands at the replication fork?
Leading and Lagging
61
# E.coli Which is the leading strand? Which is the lagging strand?
Leading strand (3') is going into the fork Lagging strand (5') is going away from the fork
62
DNA synthesis is primed using _ copied from DNA generated by _
Using RNA copied from DNA generated by primase. This gives DNA pol III a place to start
63
Which DNA pol extends the with new DNA?
DNA pol III
64
What does DNA pol 1 do to the RNA at the 5' end?
Remove the RNA and fills the gap
65
What connects the adjacent fragments after the RNA (primers) are removed?
DNA ligase
66
Normal base pairing results in...
faithful transmission of the DNA
67
Mistmatches between bases can occur, sometimes resulting in
mutations
68
# Point mutations What is a transition?
When one purine changes to the other or when one pyrimiding changes to the other
69
# Point mutations What is a transversion?
When a pyrimidine transitions to a purine or vice versa
70
What activity enables error correction?
3' to 5' exonuclease activity
71
What facilitates DNA replication on both strands?
Replisome, accessory proteins and looping
72
# Eukaryotes How do eukaryotic origins differ from e. coli origins?
Eukaryotes have multiple replication origins. Different parts of the chromosome will be replicated simultaneously
73
# Eukaryotes How does replication extend from these origins?
Bidirectionally
74
# Eukaryotes Eventually contigious, fully replicated _ are produced
Chromatids
75
# Eukaryotes When does DNA replication occur in eukaryotes?
During S phase
76
# Eukaryotes Initiation of DNA replication at the eukaryotic involves _ of specific . Such as _
Involves recruitment of specific proteins. Such as Cdc6
77
# Eukaryotes What happens after the specific proteins are recruited?
Helicase will unwind the DNA, allowing DNA polymerase to bind
78
# Eukaryotes What melts the AT regions to help binding to chromosome?
Helicase + Cdt1
79
# Eukaryotes How do you fill the gap at the teleomere in linear chromosome?
Telomerase helps extend the telomeres, fixing the gap (most of the gap)
80
# Eukaryotes What happens after the telomere is extended by telomerase? Example in humans?
Proteins bind to the end to form a cap that stabilizes the structure at the end. TRF 1 and TRF 2

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