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

Ch 12 DNA Replication & Recombination Flashcards

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

A

DNA helicase

25
Q

attach to unwound DNA and stabilize the strands in place to prevent secondary structures from forming

A

single-strand-binding proteins

26
Q

moves ahead of replication fork and reduces torsional strain that builds due to unwinding of DNA

A

DNA gyrase

27
Q

DNA gyrase is what type of topoisomerase? What does it do?

A

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
Q

explain process of bacterial elongation

A
  • 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
Q

RNA polymerase that synthesizes primers on template DNA strand to provide a 3’-OH group for attachment of DNA nucleotides

A

DNA primase

30
Q

short stretches of RNA nucleotides synthesized on template DNA strand

A

primers

31
Q

why are primers required for DNA replication?

A

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
Q

what do all DNA polymerases require in order to add nucleotides?

A

a 3’-OH group

33
Q

describe DNA polymerase III

A

elongates new nucleotide strand from 3’-OH group provided by
- 5’ –> 3’ polymerase activity (DNA synthesis)
- 3’ –> 5’ exonuclease activity (proofreading)
high processivity

34
Q

describe DNA polymerase I

A

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
Q

catalyzes formation of phosphodiester bonds between Okazaki fragments and seals breaks

A

DNA ligase

36
Q

describe process of bacterial termination

A

terminus utilization substance (Tus) binds to termination sequences and blocks helicase movement, preventing replication

37
Q

what are processes that lead to the high accuracy of DNA replication

A
  • nucleotide selection
  • proofreading
  • mismatch repair
38
Q

process of DNA polymerase particular pairing nucleotides with complements on template

A

nucleotide selection

39
Q

process of proofreading

A

DNA polymerase removes incorrect paired nucleotide and replaces it

40
Q

process of mismatch repair

A

enzymes excise incorrectly paired nucleotides and replace with correct ones AFTER replication

41
Q

binds to defined origins or replication and initiates replication

A

origin-recognition complex (orC)

42
Q

how do the origins or replication differ in eukaryotes than prokaryotes

A

eukaryotes have many, prokaryotes usually have one

43
Q

explain process of eukaryotic initiation

A
  • replication licensing factors attach to origins to license and approve them for replication
  • initiator proteins bind
44
Q

explain process of eukaryotic unwinding

A

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

45
Q

describe DNA polymerase α

A

has primase activity and synthesizes RNA primers

46
Q

describe DNA polymerase δ

A

synthesizes lagging strand

47
Q

describe DNA polymerase ε

A

synthesizes leading strand

48
Q

explain nucleosome assembly in eukaryotic replication

A
  • original nucleosomes disrupted
  • old histones redistributed onto new DNA
  • new histones synthesized and added to form new nucleosomes
49
Q

what organisms face end-replication problem and why?

A

eukaryotes face end-replication problems because they have linear DNA

50
Q

describe the end replication problem

A

DNA replication leaves gaps at end of chromosomes due to removal of terminal primers

51
Q

sequences at the end of chromosomes that have many copies of short repeated sequences (G-rich overhang TTAGGG)

A

telomeres

52
Q

enzyme that prevents shortening of chromosomes by extending sequence

A

telomerase

53
Q

what cells would telomerase most likely be found in?

A

stem cells and germ cells

54
Q

single-stranded protruding end of telomere

A

G-rich overhang

55
Q

describe how telomerase extends DNA to fill in gaps at ends of chromosomes

A
  • 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
Q

what types of problems could lack of telomerase in a cell cause?

A

progressive shortening of chromosomes and premature aging

57
Q

what types of problems could overabundance of telomerase in a cell cause?

A

promotion of cancer

58
Q

homologous combination

A

exchange of genetic information between homologous chromosomes

59
Q

summary of the Holliday model of homologous recombination

A
  • 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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