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Microbiology > Ch. 10 > Flashcards

Ch. 10 Flashcards

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1
Q

Mutation -

A

Heritable change in DNA sequence that can lead to a change in phenotype

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2
Q

Phenotype -

A

Observable properties of an organism

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3
Q

Mutant -

A

A strain of any cell or virus differing from parental strain in genotype

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4
Q

Genotype -

A

Nucleotide sequence of genome

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5
Q

Wild-type strain -

A

Typically refers to strain isolated from nature

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6
Q

Selectable mutations -

A
  • those that give the mutant a growth advantage under certain conditions
  • useful in genetic research
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7
Q

Nonselectable mutations -

A
  • those that usually have neither an advantage not a disadvantage over the parent
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8
Q

Detecting such mutations requires examining a large number of colonies and looking for differences -

A

Screening

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9
Q

Antibiotic resistance is an easy ___ marker.

A

Selectable

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10
Q

UV-radiation-induced nonpigmented mutants of Serratia marcescens is a ___ mutation.

A

Nonselectable

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11
Q

Halobacterium, a member of Archaea.

White colonies are the ___ and orangish-brown colonies are mutants that lack gas vesicles.

A

Wild-type

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12
Q

___ is always more tedious than selection.

A

Screening

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13
Q

Methods are available to facilitate screening:

A

Ex. Replica plating

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14
Q

___ ___ is useful for identifying cells with a nutritional requirement for growth.

A

Replica plating

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15
Q

Auxotroph -

A

An organism that has developed a nutritional requirement through mutation

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16
Q

A ___ is a parent from which an auxotroph mutant has been derived.

A

Prototroph

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17
Q

Induced mutations -

A
  • those made environmentally or deliberately

- can result from exposure to natural radiation or oxygen radicals

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18
Q

Spontaneous mutations -

A

Those that occur without external intervention (occasional errors due to DNA polymerase during replication)

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19
Q

Point mutations -

A
  • mutations that change only one base pair

- can lead to a single amino acid change in a protein, an incomplete protein, or no change at all

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20
Q

Silent mutation -

A

Does not affect amino acid sequence

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21
Q

Missense mutation -

A

Amino acid changed; polypeptide altered

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22
Q

Nonsense mutation -

A

Codon becomes stop codon; polypeptide is incomplete

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23
Q

___ and ___ cause more dramatic changes in DNA.

A

Deletions and insertions

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24
Q

Frameshift mutations -

A
  • deletions or insertions that result in a shift in the reading frame
  • often result in complete loss of gene function
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25
Q

What often result in complete loss of gene function?

A

Frameshift mutations

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26
Q

Point mutations are typically ___.

A

Reversible

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27
Q

Reversion -

A

Alteration in DNA that reverses the effects of a prior mutation

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28
Q

Revertant -

A

Strain in which original phenotype is restored

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29
Q

Two types of revertant:

A
  • same-site revertant

- second-site revertant

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30
Q

Same-site revertant -

A

Mutation is at the same site as original mutation

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31
Q

Second-site mutation -

A

Mutation is at a different site in the DNA

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32
Q

Suppressor -

A

Mutation that compensates for the effect of the original mutation

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33
Q

For most microorganisms, errors in DNA replication occur at a frequency of ..

A

10^-6 to 10^-7 per kilobase

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34
Q

DNA viruses have error rates ____ greater.

A

100-1000X

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35
Q

The mutation rate in RNA genomes is ___ higher than in DNA genomes.

A

1000-fold

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36
Q

Some RNA polymerases have ___ capabilities.

A

Proofreading

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37
Q

RNA ___ ___ similar to DNA ___ ___ do not exist.

A

Repair mechanisms

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38
Q

The ___ ___ makes practical use of bacterial mutations to detect for potentially hazardous chemicals.

A

Ames test

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39
Q

The Ames test

A
  • looks for an increase in mutation of bacteria in the presence of suspected mutagen
  • a wide variety of chemicals have been screened for toxicity and carcinogenicity
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40
Q

Mutagens -

A

Chemical, physical, or biological agents that increase mutation rates

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41
Q

Nucleotide base analogs -

A

Resemble nucleotides

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42
Q

Chemical mutagens that induce chemical modifications

A

Ex. Alkylating agents such as nitrosoguanidine

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43
Q

Chemical mutagens that cause frameshift mutations

A

Ex. Intercalating agents such as acridines and Ethidium Bromide

44
Q

Two main categories of mutagenic electromagnetic radiation:

A
  • nonionizing

- ionizing

45
Q

Nonionizing:

A
  • purines and pyrimidines strongly absorb UV

- pyrimidine dimer is one effect of UV radiation

46
Q

Example of nonionizing

A

UV radiation

47
Q

Ionizing:

A
  • more powerful than UV radiation
  • ionize water and produce free radicals
  • free radicals damage macromolecules in the cell
48
Q

Example of ionizing

A
  • x-rays
  • cosmic rays
  • gamma rays
49
Q

Three types of DNA repair systems:

A
  • direct reversal
  • repair of single-strand damage
  • repair of double-strand damage
50
Q

Direct reversal -

A

Mutated base is still recognizable and can be repaired without referring to other strand

51
Q

Repair of single-strand damage -

A

Damaged DNA is removed and repaired using opposite strand as template

52
Q

Repair of double-strand damage -

A

A break in the DNA

- requires more error-prone repair mechanisms

53
Q

Perfect ___ in organisms is counterproductive because it prevents evolution.

A

Fidelity

54
Q

The ___ ___ of an organism is subject to change.

A

Mutation rate

55
Q

Mutator strains -

A

Bacteria that benefit from increased mutation rates

56
Q

Mutants can be isolated that are ___ or have __ mutation rates.

A

Hyperaccurate; increased

57
Q

Recombination -

A

Physical exchange of DNA between genetic elements

58
Q

Homologous recombination -

A

Process that results in genetic exchange between homologous DNA from two different sources

59
Q

___ ___ can be used to detect rare genetic recombinants.

A

Selective medium

60
Q

Transformation -

A

Genetic transfer process by which DNA is incorporated into a recipient cell and brings about genetic change

61
Q

Competent -

A

Cells are capable of taking up DNA and being transformed

62
Q

In naturally transformable bacteria, ___ is regulated.

A

Competence

63
Q

Electroporation -

A

Electricity can be used to force cells to take up DNA.

64
Q

During ___ ___, integration of transforming DNA is a highly regulated, multi step process.

A

Natural transformation

65
Q

Transfection -

A

Transformation of bacteria with DNA extracted from a bacterial virus

66
Q

___ is a physical technique that is used to get DNA into organisms that are difficult to transform.

A

Electroporation

67
Q

Electroporation:

A

Cells are mixed with DNA and then exposed to brief high-voltage electrical pulses, which makes the cell envelope permeable and allows entry of the DNA

68
Q

Transduction-

A

Transfer of DNA from one cell to another by a bacteriophage

69
Q

Two modes of transduction:

A

Generalized transduction

Specialized transduction

70
Q

Generalized transduction -

A

DNA from any portion of the host genome is packaged inside the virion

  • defective virus particle incorporates fragment of the cells chromosome randomly
  • virus can be temperate or virulent
  • low efficiency
71
Q

Specialized transduction -

A

DNA from a specific region of the host chromosome is integrated directly into the virus genome

  • DNA of temperate virus excises incorrectly and takes adjacent host genes along with it
  • transducing efficiency can be high
72
Q

Phage conversion-

A

Alteration of the phenotype of a host cell by lysogenization

73
Q

Nondefective temperate phage lysogenizes a cell and becomes a ___.

A

Prophage

74
Q

Bacterial conjugation (mating) -

A

Mechanism of genetic transfer that involves cell-to-cell contact

  • plasmid-encoded mechanism
75
Q

Donor cell -

A

Contains conjugative plasmid

76
Q

Recipient cell -

A

Does not contain plasmid

77
Q

F (fertility) plasmid -

A
  • circular DNA molecule; about 100 kpb
  • contains genes that regulate DNA replication
  • contains several transposable elements that allows the plasmid to integrate into the host chromosome
  • contains tra genes that encode transfer functions
78
Q

___ ___ is essential for conjugation.

A

Sex pilus

79
Q

DNA ___ is necessary for DNA transfer by conjugation.

A

Synthesis

80
Q

DNA synthesized by ___ ___ ___.

A

Rolling circle replication

81
Q

F plasmid is a ___; can integrate into host chromosome

A

Episome

82
Q

Cells possessing a nonintegrated F plasmid are called ___.

A

F+

83
Q

Cells possessing an integrated F plasmid are called ___.

A

Hfr (high frequency of recombination)

84
Q

Presence of the F plasmid results in alterations of cell properties:

A
  • ability to synthesize F pilus
  • mobilization of DNA for transfer to another cell
  • alteration of surface receptors so that cell can no longer act as a recipient in conjugation
85
Q

___ ___ (mobile elements) are present in both the F plasmid and E. coil chromosome.

A

Insertion sequences

86
Q

Plasmid is now part of ___.

A

Chromosome

87
Q

Chromosomal genes transferred with ___.

A

Plasmid

88
Q

Recipient cell does not become Hfr because …

A

Only a portion of the integrated F plasmid is transferred by the donor

89
Q

Hfr strains that differ in the __ __ of the F plasmid in the chromosome transfer genes in different orders.

A

Integration position

90
Q

Genetic crosses with __ __ can be used to map the order of genes on the chromosome.

A

Hfr strains

91
Q

F’ plasmids -

A

Previously integrated F plasmids that have excised and captured some chromosomal genes

92
Q

Discrete segments of DNA that move as a unit from one location to another within other DNA molecules are ___ ___.

A

Transposable elements

93
Q

Transposable elements can be found in all three..

A

Domains of life

94
Q

Transposable elements move by a process called ___.

A

Transposition

95
Q

Transposition was first observed by who?

A

Barbara McClintock

96
Q

Two main types of transposable elements in bacteria are ___ and ___ ___.

A

Transposons and insertion sequences

97
Q

Transposons and insertion sequences

A
  • both carry genes encoding transposase

- both have inverted repeats at their ends

98
Q

___ ___ are the simplest transposable element.

A

Insertion sequences

99
Q

Insertion sequences:

A
  • about 1000 nucleotides long
  • inverted repeats are 10-50 base pairs
  • only gene is for the transposase
  • found in plasmids and chromosomes of bacteria and archaea
  • found in some bacteriophages
100
Q

___ are larger than insertion sequences.

A

Transposons

101
Q

Transposons:

A
  • transposase moves any DNA between inverted repeats
  • insertion of a transposable element generates a duplicate target sequence
  • may include antibiotic resistance
102
Q

Two types of mechanisms of transposition:

A
  • conservative

- replicative

103
Q

Conservative -

A

Transposon is excised from one location and reinserted at a second location
- number of transposons stays constant

104
Q

Replicative -

A

A new copy of transposon is produced and inserted at a second location

  • number of transposons present doubles
105
Q

Cells capable of growing on selective medium likely acquired ___.

A

Transposon

Microbiology (26 decks)

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