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BIOL 2320 - Genetics > DNA Replication > Flashcards

DNA Replication Flashcards

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1
Q

What composes a DNA polymer?

A

nucleotide monomers

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2
Q

Describe the structure of a DNA nucleotide

A

a 5-carbon sugar (deoxyribose)

one of four nitrogenous bases (A, G, C, T)

up to 3 phosphate groups

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3
Q

What is the sugar in DNA nucleotides?

A

deoxyribose

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4
Q

How many sugars does the deoxyribose have?

A

5

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5
Q

What is bonded to the 1’ carbon of the deoxyribose?

A

a nucleotide base

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6
Q

What is bonded to the 3’ carbon of the deoxyribose?

A

a hydroxyl group

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7
Q

What is bonded to the 5’ carbon of the deoxyribose?

A

1-3 phosphates

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8
Q

What are the 2 types of DNA bases?

A

pyrimidines

purines

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9
Q

Describe the structure of pyrimidine

A

a single ring

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10
Q

Describe the structure of purines

A

a double ring

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11
Q

Which nitrogenous bases are pyrimidines?

A

C and T

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12
Q

Which nitrogenous bases are purines?

A

A and G

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13
Q

What assembles nucleotides into a polymer?

A

DNA polymerase

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14
Q

How does DNAP assemble a polymer?

A

DNAP catalyzes the formation of covalent bonds between the 3’ OH and 5’ phosphate group

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15
Q

What is the name of the covalent bond that forms between the 3’ OH and 5’ phosphates?

A

phosphodiester bonds

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16
Q

What type of backbone does each polynucleotide chain have?

A

a sugar-phosphate backbone

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17
Q

T or F: the two polynucleotide chains are complementary

A

True

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18
Q

T or F: the two polynucleotide chains are antiparallel

A

True

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19
Q

Which nitrogenous bases pair together in complementary pairing?

A

C - G

A - T

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20
Q

What are 3 attributes of DNA replication?

A
  1. each strand of the parental DNA molecule remains intact during replication
  2. each parental strand serves as a template for formation of a daughter strand
  3. result = formation of 2 identical daughter duplexes composed of one parental and one daughter strand
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21
Q

T or F: the covalent bonds holding monomers together are broken during replication

A

FALSE they’re never broken

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22
Q

T or F: each strand of the parental DNA molecule is altered during replication

A

false, they remain intact

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23
Q

What do the parental strands serve during replication?

A

as a template for a daughter strand

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24
Q

Describe a daughter DNA strand

A

produced by DNA replication of the parental DNA and is complementary and antiparallel

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25
Q

When does DNA replication occur (in the cell cycle)?

A

In S phase (DNA synthesis)

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26
Q

Which 6 macromolecules are involved in DNA replication?

A 
helicase
single strand binding protein
DNAPIII
Primase
DNAPI
Ligase
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27
Q

Where does DNA replication start?

A

the origins of replication (ori)

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28
Q

How does replication start?

A

proteins recognize ori DNA sequences and separate DNA strands to form a replication bubble

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29
Q

How does a replication bubble form?

A

When proteins recognize the ori DNA sequences and separate the DNA strands

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30
Q

What direction does DNA replication occur in relation to the origin?

A

bi-directionally (both ways)

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31
Q

What direction are strands always replicated? And what end are all nucleotides added to?

A

5’ - 3’

nucleotides always added at 3’

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32
Q

What occurs at each end of a replication bubble?

A

replication forks

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33
Q

What enzyme functions at the replication forks? What does it do?

A

helicase unwinds and separates DNA strands

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34
Q

What holds the DNA strands apart after they are separated and until they are replicated?

A

Single Stranded Binding Proteins (SSBPs)

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35
Q

What happens once a single stranded DNA template forms?

A

Primase synthesizes a short RNA primer

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36
Q

What is the function of primase?

A

it synthesizes a short RNA primer after a single stranded DNA template forms

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37
Q

What is the main enzyme of DNA replication?

A

DNAPIII

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38
Q

What does DNAPIII require to add nucleotides?

A

a primer

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39
Q

What is the function of DNAPIII?

A

catalyzes synthesis by elongating RNA primers by adding nucleotides complementary to template strand

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40
Q

What direction does DNAPIII catalyze synthesis?

A

5’ - 3’

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41
Q

What kind of nuclease activity does DNAPIII have?

A

3’ - 5’ exonuclease

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42
Q

What direction does DNAPIII have exonuclease activity?

A

3’ to 5’

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43
Q

What is the purpose of the 3’ - 5’ exonuclease activity of DNAPIII?

A

it allows it to remove mismatched bases

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44
Q

What is the function of DNAPI?

A

it removes RNA primers and fills in the resulting gap with DNA

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45
Q

What type of nuclease activity does DNAPI have?

A

5’ - 3’ exonuclease activity

THIS IS UNCLEAR IN SLIDES?

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46
Q

What direction does DNAPI catalyze chain growth?

A

5’ - 3’

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47
Q

What occurs after DNAPI removes the RNA primer and fills in the gap with DNA?

A

DNA ligase links the DNA fragments together by catalyzing the formation of phosphodiester bonds

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48
Q

Which enzyme links DNA fragments together after DNAPI adds the DNA?

A

DNA Ligase

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49
Q

As the DNA strands unwind, how many template strands are there?

A

2

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50
Q

Describe the leading strand

A

one of the template strands that is elongated in the same direction of the unwinding DNA
(5’ to 3’)

51
Q

Describe the lagging strand

A

one of the template strands that elongates away from the replication fork (3’- 5’)

52
Q

How is the leading strand synthesized?

A

continuously

53
Q

How many RNA primers does the synthesis of the leading strand require?

A

one RNA primer

54
Q

How is the lagging strand synthesized?

A

discontinuously

55
Q

How many RNA primers does the synthesis of the lagging strand require?

A

many RNA primers

56
Q

Describe Okazaki fragments

A

the short fragments synthesized on lagging strand

57
Q

How are Okazaki fragments linked together?

A

by Ligase

58
Q

How many origin of replications do prokaryotes have?

A

1

59
Q

Describe prokaryotic chromosomes

A

they have only one small circular chromosome

60
Q

Describe eukaryotic chromosomes

A

they have long linear chromosomes

61
Q

How many origins or replication does each eukaryotic chromosome have?

A

many

62
Q

What happens if DNAPI is not properly functioning and the DNA cannot be filled in after the primer is removed from the leading strand?

A

chromosomes are shortened = loss of DNA sequences at the end of chromosomesc

63
Q

How can loss of DNA sequences at the end of chromosomes be prevented?

A

by adding multiple copies of simple noncoding sequences to DNA at the chromosome ends

64
Q

Describe telomerase

A

an enzyme that adds multiple copies of simple noncoding sequences to 3’ ends of DNA molecules

65
Q

Which end of DNA molecules does telomerase add copies of noncoding sequences?

A

3’ end

66
Q

Describe telomeres

A

The regions on a DNA molecule that form when telomerase adds multiple copies of noncoding sequences to the 3’ ends

67
Q

Which cells is telomerase functional in?

A

germ line cells

68
Q

What would happen to somatic cells each time they divide if telomerase wasn’t present?

A

their chromosomes would shorten with each division

69
Q

How do telomeres preserve chromosome integrity?

A

they associate with proteins to form protective caps that prevent the degradation of linear chromosomes

70
Q

What are the 5 essential characteristics known about DNA before it was identified as the hereditary molecule?

A
  1. localized to the nucleus and a component of chromosomes
  2. present in stable form in cells
  3. complex and contains info needed for structure, function, development and reproduction of an organism
  4. ability to accurately replicate itself so that daughter cell contains same information as parent cells
  5. mutable - undergoes a low rate of mutants that introduce genetic variation which is the basis for evolutionary change
71
Q

Where is DNA localized? What is it a component of?

A

to the nucleus

component of chromosomes

72
Q

In what form is DNA present in cells?

A

stable form

73
Q

what information does DNA contain?

A

info for structure, function, development and reproduction of an organism

74
Q

T or F: DNA can accurately replicate itself so that the daughter cells have the same info as the parent cells

A

true

75
Q

What is the basis for evolutionary change?

A

the low rate of mutations of DNA that introduce genetic variation

76
Q

What did Griffith’s experiment discover?

A

the process of transformation

77
Q

Describe transformation

A

the genetic alteration of a cell by the uptake of isolated pieces of external DNA

DNA in environment is taken into bacterial cell and incorporated into its genome

78
Q

What organisms did Griffith use in his 1928 experiment?

A

Pneumococcal bacteria and mice

79
Q

What two strains of Pneumococcal bacteria did Griffith identify in his 1928 experiment?

A

S (smooth) strain

R (rough) strain

80
Q

In Griffith’s experiment, what did the two Pneumococcal bacterial strains cause in the mice?

A

smooth (S) = caused pneumonia in mice

rough (R) = did not cause pneumonia in mice

81
Q

What was Griffith’s experiment?

A

he infected mice with Pneumococcal bacteria to determine whether the mice could take up the bacterial DNA and get pneumonia

82
Q

What happened to the mice that were infected with Pneumococcal strain S?

A

they got pneumonia and died

83
Q

What happened to the mice that were infected with Pneumococcal live strain R OR heat-killed strain S?

A

they survived

84
Q

What happened to the mice infected with heat-killed strain S AND live strain R?

A

they developed pneumonia and died

85
Q

What was recovered from the mice that were injected with heat killed strain S AND live strain R?

A

live type S bacteria

86
Q

What can be concluded from the Griffith’s experiment?

A

the hereditary molecule (DNA) in mice ‘transformed’ the live R strain bacteria into live S strain bacterial

87
Q

Describe the experiment by Avery, MacLeod, and McCarty

A

they infected mice with extracts from heat-killed S bacteria and live R bacteria

88
Q

What was the purpose of the extract from heat-killed S bacteria? (Avery, MacLeod, McCarty)

A

it was divided into aliquots and treated to destroy either DNA, RNA, proteins, lipids, polysaccharides

89
Q

In Avery et al., study, what was injected into the mice?

A

one of the aliquots with treated heat-killed S bacteria and live R bacteria

90
Q

What were the results of the Avery et al. study?

A

all aliquots killed the mice except the one with destroyed DNA

91
Q

What was the significance of the experiment by Avery, MacLeod and McCarty?

A

they identified DNA as the most likely hereditary molecule

92
Q

What did Hershey and Chase’s experiment show?

A

that DNA is responsible for bacteriophage infection of bacterial cells

93
Q

What are bacteriophages?

A

viruses that infect bacteria

94
Q

What was unique about the bacteriophages used in Hershey and Chase’s experiment?

A

the phages had a protein shell with a tail segment that attaches to the host cell and a head that contains DNA

95
Q

Describe the phages used in the Hershey and Chase experiment

A

the phages have a protein shell with a tail segment that attaches to the host cell

and a head that contains DNA

96
Q

How do phages reproduce?

A

by infecting bacterial hosts

97
Q

When does phage infection begin in bacteria?

A

when the phage injects DNA into the bacterial cell and leaves its protein shell on the surface

98
Q

What happens after the phage has injected DNA into the bacterial cell and leaves its protein shell?

A

the phage DNA replicates in the bacterium and produces proteins that are assembled into progeny phage

99
Q

How are progeny phage produced?

A

the phage DNA replicates in the bacterium and produces proteins

these proteins are assembled into the progeny phage

100
Q

How are progeny phage released from the host cell?

A

lysis of the host cell

101
Q

What does protein contain large amounts of?

A

sulfur

102
Q

What does protein contain almost nothing of?

A

phosphorous

103
Q

What does DNA contain large amounts of?

A

phosphorous

104
Q

What does DNA contain none of?

A

sulfur

105
Q

How did Hershey and Chase collect the results for their experiment?

A

they labelled phage protein with 35^S or phage DNA with 32^P and traced them during the course of infection

106
Q

How did Hershey and Chase separate the empty phage particles from the injected bacteria?

A

infection agitation by using a blender

107
Q

What was detected by Hershey and Chase in the protein labelling experiment?

A

radioactivity in the empty phage particles

108
Q

What was detected by Hershey and Chase in the DNA labelling experiment?

A

radioactivity in the infected bacteria

109
Q

Who identified the secondary helical structure of DNA?

A

Franklin

110
Q

Who modelled the secondary helical structure of DNA?

A

Watson and Crick

111
Q

Describe the structure of DNA

A

composed of four kinds of nucleotides joined by covalent phosphodiester bonds with 2 polynucleotide chains that come together to form a double helix

112
Q

What is the type of bond that joins nucleotides to make a DNA polymer?

A

covalent phosphodiester bonds

113
Q

How many competing models of DNA replication are there?

A

3

114
Q

What is common across the 3 competing models of DNA replication?

A

the idea that the original strands of the duplex act as templates for the daughter strand synthesis

115
Q

What are the 3 models of DNA replication?

A

semiconservative

conservative

dispersive

116
Q

Describe semiconservative DNA replication

A

each daughter duplex contains one parental and one daughter strand

117
Q

Describe conservative DNA replication

A

one daughter duplex contains both parental strands and the other daughter duplex contains both daughter strands

118
Q

Describe dispersive DNA replication

A

each daughter duplex contains interspersed parental and daughter segments

119
Q

Describe the Meselson-Stahl experiment

A

they used cesium chloride centrifugation to separate molecules with different weights to test the models of DNA replication

120
Q

What organism did Meselson-Stahl use? What did they grow it in?

A

they grew E. coli in a medium containing heavy nitrogen

121
Q

What did Meselson-Stahl do after all the E.coli had DNA containing heavy nitrogen only?

A

they transferred it to Nitrogen-14 and allowed one round of replication

122
Q

After replication of E.coli cells, what did Meselson and Stahl do?

A

they isolated the DNA of a small amount of cells and centrifuged it to determine its density

123
Q

What were the results of the Meselson-Stahl experiment?

A

after 1 replication: DNA molecules had the densities expected

after 2 rounds: half the molecules had expected densities

BIOL 2320 - Genetics (12 decks)

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