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Genetics - BIO 2306 > Ch 12 DNA Replication & Recombination > Flashcards

Ch 12 DNA Replication & Recombination Flashcards

(59 cards)

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1
Q

model of replication:
- two nucleotide strands separate and each serves as a template for synthesis of a new strand
- original strands stays intact but does not combine into same molecule

A

semiconservative replication

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2
Q

model of replication:
- entire dsDNA serves as template for new DNA molecule

A

conservative replication

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3
Q

model of replication:
- both nucleotide strands broken into fragments and reassemble into new DNA molecules
- each DNA molecule has interspersed original and new DNA

A

dispersive replication

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4
Q

what did Meselson and Stahl’s experiment determine was the correct mode of replication?

A

their experiment determined semiconservative replication was the right model

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5
Q

characteristics of theta replication model (DNA template, breakage of nucleotide strand, origin of replications, directions, products)

A
  • circular DNA
  • no breakage
  • one origin of replication
  • unidirectional or bidirectional
  • two circular DNA products
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6
Q

characteristics of rolling circle model (DNA template, breakage of nucleotide strand, origin of replications, directions, products)

A
  • circular DNA
  • breakage in single strand
  • one origin of replication
  • unidirectional
  • one circular and one linear DNA product (that can circulize to produce more)
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7
Q

characteristics of linear eukaryotic model (DNA template, breakage of nucleotide strand, origin of replications, directions, products)

A
  • linear DNA
  • no breakage
  • multiple origins of replications
  • bidirectional
  • two linear DNA products
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8
Q

Requirements for DNA replication

A
  • single-stranded DNA template
  • raw materials (substrates) to be assembled into new nucleotide strand (dNTPs)
  • enzymes & proteins that read the template and assemble the new strand
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9
Q

what are the substrates that are assembled into a new nucleotide strand during DNA replication?

A

deoxyribonucleoside triphosphates (dNTPs)

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10
Q

how are the substrates assembled into a new nucleotide strand during DNA replication?

A

dNTPs bonds with the 3-OH of previous nucleotide, cleaving off two phosphates, and a phosphodiester bond forms between the two nucleotides

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11
Q

in what direction is DNA replication?

A

5’ –> 3’
nucleotides added only to 3’ end of growing strand

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12
Q

enzymes that synthesize DNA

A

DNA polymerases

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13
Q

strand synthesized during replication that is continuous

A

leading strand

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14
Q

what strand does the template strand exposed in the 3’ –> 5’ direction synthesize?

A

it synthesizes the leading strand

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15
Q

strand synthesized during replication that is discontinuous

A

lagging strand

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16
Q

what strand does the template strand exposed in the 5’ –> 3’ direction synthesize?

A

it synthesizes the lagging strand

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17
Q

fragments of lagging strand that are linked together to create a continuous new DNA molecule

A

Okazaki fragments

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18
Q

does synthesis of leading strand go towards or opposite of replication fork unwinding?

A

synthesis of leading strand goes towards replication fork unwinding

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19
Q

does synthesis of lagging strand go towards or opposite of replication fork unwinding?

A

synthesis of leading strand goes opposite of replication fork unwinding

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20
Q

four stages of bacterial DNA replication:

A

initiation, unwinding, elongation, termination

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21
Q

binds to origin of replication (oriC) and separates DNA strands to initiate replication

A

initiator protein

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22
Q

explain process of bacterial initiation

A

initiator proteins bind to origin of replication (oriC), causing short section of DNA to unwind

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23
Q

explain process of bacterial unwinding

A

unwinding proteins (DNA helicase, single-strand-binding proteins, and DNA gyrase) bind to DNA to assist in unwinding

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24
Q

breaks hydrogen bonds between nucleotide bases and unwinds DNA at replication fork

25
attach to unwound DNA and stabilize the strands in place to prevent secondary structures from forming
single-strand-binding proteins
26
moves ahead of replication fork and reduces torsional strain that builds due to unwinding of DNA
DNA gyrase
27
DNA gyrase is what type of topoisomerase? What does it do?
type II topoisomerase - makes double-strand break in segment of DNA helix - passes one segment through the break - reseals broken ends of DNA back together
28
explain process of bacterial elongation
- primase synthesizes RNA primers for DNA polymerase to add DNA molecules onto - DNA polymerase III synthesizes DNA on leading and lagging strand - DNA polymerase I removes and replaces primers - DNA ligase seals breaks of Okazaki fragments
29
RNA polymerase that synthesizes primers on template DNA strand to provide a 3'-OH group for attachment of DNA nucleotides
DNA primase
30
short stretches of RNA nucleotides synthesized on template DNA strand
primers
31
why are primers required for DNA replication?
for DNA synthesis, all DNA polymerases require a 3'-OH group in order to add a nucleotide. DNA doesn't have 3'-OH group, so primase synthesizes primers, which provide a 3'-OH group for DNA polymerases to add DNA nucleotides on
32
what do all DNA polymerases require in order to add nucleotides?
a 3'-OH group
33
describe DNA polymerase III
elongates new nucleotide strand from 3'-OH group provided by - 5' --> 3' polymerase activity (DNA synthesis) - 3' --> 5' exonuclease activity (proofreading) high processivity
34
describe DNA polymerase I
removes and replaces RNA primers with DNA - 5' --> 3' polymerase activity (DNA synthesis) - 3' --> 5' exonuclease activity (proofreading) - 5' --> 3' exonuclease activity (remove primers)
35
catalyzes formation of phosphodiester bonds between Okazaki fragments and seals breaks
DNA ligase
36
describe process of bacterial termination
terminus utilization substance (Tus) binds to termination sequences and blocks helicase movement, preventing replication
37
what are processes that lead to the high accuracy of DNA replication
- nucleotide selection - proofreading - mismatch repair
38
process of DNA polymerase particular pairing nucleotides with complements on template
nucleotide selection
39
process of proofreading
DNA polymerase removes incorrect paired nucleotide and replaces it
40
process of mismatch repair
enzymes excise incorrectly paired nucleotides and replace with correct ones AFTER replication
41
binds to defined origins or replication and initiates replication
origin-recognition complex (orC)
42
how do the origins or replication differ in eukaryotes than prokaryotes
eukaryotes have many, prokaryotes usually have one
43
explain process of eukaryotic initiation
- replication licensing factors attach to origins to license and approve them for replication - initiator proteins bind
44
explain process of eukaryotic unwinding
unwinding proteins (DNA helicase, single-strand-binding proteins, and topoisomerases) bind to DNA to assist in unwinding
45
describe DNA polymerase α
has primase activity and synthesizes RNA primers
46
describe DNA polymerase δ
synthesizes lagging strand
47
describe DNA polymerase ε
synthesizes leading strand
48
explain nucleosome assembly in eukaryotic replication
- original nucleosomes disrupted - old histones redistributed onto new DNA - new histones synthesized and added to form new nucleosomes
49
what organisms face end-replication problem and why?
eukaryotes face end-replication problems because they have linear DNA
50
describe the end replication problem
DNA replication leaves gaps at end of chromosomes due to removal of terminal primers
51
sequences at the end of chromosomes that have many copies of short repeated sequences (G-rich overhang TTAGGG)
telomeres
52
enzyme that prevents shortening of chromosomes by extending sequence
telomerase
53
what cells would telomerase most likely be found in?
stem cells and germ cells
54
single-stranded protruding end of telomere
G-rich overhang
55
describe how telomerase extends DNA to fill in gaps at ends of chromosomes
- telomerase base pairs with G-rich strand, and provides template for nucleotide synthesis - nucleotides are added to 3' end of G-rich strand - telomerase moves along DNA so more nucleotides could be added
56
what types of problems could lack of telomerase in a cell cause?
progressive shortening of chromosomes and premature aging
57
what types of problems could overabundance of telomerase in a cell cause?
promotion of cancer
58
homologous combination
exchange of genetic information between homologous chromosomes
59
summary of the Holliday model of homologous recombination
- single-strand breaks occur in homologous chromosomes - strand invasion to broken end of other DNA - Holliday junction formation - branch migration

Genetics - BIO 2306 (20 decks)

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