Biochemistry Reginald H. Garrett 5th Edition Test Bank

Brock Biology of Microorganisms Michael T. Madigan 13th Edition Test Bank

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Title : Brock Biology of Microorganisms

Author : Michael T. Madigan

Edition : 13th Edition

Type : TestBank

Product Description

Brock Biology of Microorganisms Michael T. Madigan 13th Edition Test Bank

Brock Biology of Microorganisms Michael T. Madigan 13th Edition Test Bank

 

Sample

Chapter 10

MULTIPLE CHOICE.  Choose the one alternative that best completes the statement or answers the question.


1)
 

A mutant that has a nutritional requirement for growth is an example of a(n)
 

1)
 

_______

 

  1. A)

 

auxotroph.
 

  1. B)

 

heterotroph.
 

  1. C)

 

autotroph.
 

  1. D)

 

organotroph.

 

 

 

2)
 

Consider a mutation in which the change is from UAC to UAU. Both codons specify the amino acid tyrosine. Which type of point mutation is this?
 

2)
 

_______

 

  1. A)

 

missense mutation
 

  1. B)

 

silent mutation

 

  1. C)

 

frameshift mutation
 

  1. D)

 

nonsense mutation

 

 

 

3)
 

A mutation that readily reverses to restore the original parental type would most likely be due to a(n)
 

3)
 

_______

 

  1. A)

 

point mutation.
 

  1. B)

 

deletion.

 

  1. C)

 

insertion.
 

  1. D)

 

frameshift mutation.

 

 

 

4)
 

Which process involves the formation of Holliday junctions?
 

4)
 

_______

 

  1. A)

 

transduction
 

  1. B)

 

transformation

 

  1. C)

 

conjugation
 

  1. D)

 

homologous recombination

 

 

 

5)
 

The mutagens 2-aminopurine and 5-bromouracil are examples of
 

5)
 

_______

 

  1. A)

 

nucleotide base analogs.
 

  1. B)

 

alkylating agents.

 

  1. C)

 

chemicals reacting with DNA.
 

  1. D)

 

none of the above.

 

 

 

6)
 

The killing of cells by UV irradiation involves
 

6)
 

_______

 

  1. A)

 

formation of pyrimidine dimers.
 

  1. B)

 

formation of purine dimers.

 

  1. C)

 

absorption at 260 nm by proteins only.
 

  1. D)

 

absorption at 260 nm by RNA only.

 

 

 

7)
 

Ionizing radiation does NOT include
 

7)
 

_______

 

  1. A)

 

X-rays.
 

  1. B)

 

gamma rays.
 

  1. C)

 

cosmic rays.
 

  1. D)

 

UV rays.

 

 

 

8)
 

Which of the following methods may introduce foreign DNA into a recipient?
 

8)
 

_______

 

  1. A)

 

transformation
 

  1. B)

 

conjugation
 

  1. C)

 

transduction
 

  1. D)

 

all of the above

 

 

 

9)
 

The uptake of DNA released from a cell would most likely be the result of ________, while cell-to-cell contact would most likely result in ________.
 

9)
 

_______

 

  1. A)

 

transformation / transduction
 

  1. B)

 

transformation / conjugation

 

  1. C)

 

transduction / conjugation
 

  1. D)

 

conjugation / transformation

 

 

 

10)
 

Which of the following proteins is NOT required for homologous recombination?
 

10)
 

______

 

  1. A)

 

endonuclease
 

  1. B)

 

proteins having helicase activity

 

  1. C)

 

RecA
 

  1. D)

 

Hfr

 

 

 

11)
 

Consider the following experiment. First, large populations of two mutant strains of Escherichia coli are mixed, each requiring a different, single amino acid. After plating them onto a minimal medium, 45 colonies grew. Which of the following may explain this result?
 

11)
 

______

 

  1. A)

 

The colonies may be due to recombination.

 

  1. B)

 

The colonies may be due to back mutation (reversion).

 

  1. C)

 

Either A or B is possible.

 

  1. D)

 

Neither A nor B is possible.

 

 

 

12)
 

You have performed the following mating experiment using Hfr and F- strains of Escherichia coli:

Hfr (thr+ leu+ gal+ strs) × F- (thr- leu- gal- strr). Which of the following selective media would you use to score recombinant colonies?
 

12)
 

______

 

  1. A)

 

minimal medium + streptomycin

 

  1. B)

 

minimal medium

 

  1. C)

 

minimal medium + appropriate nutrient

 

  1. D)

 

minimal medium + streptomycin + appropriate nutrient

 

 

 

13)
 

Drug resistance among enteric bacteria is spread rapidly by
 

13)
 

______

 

  1. A)

 

bacteriophages.
 

  1. B)

 

selection of mutants.

 

  1. C)

 

conjugative plasmids.
 

  1. D)

 

selective transmission.

 

 

 

14)
 

The positions of genes on a genetic map are marked according to
 

14)
 

______

 

  1. A)

 

degrees.
 

  1. B)

 

minutes.
 

  1. C)

 

nanometers.
 

  1. D)

 

radians.

 

 

 

15)
 

The minimal amount of genetic information required for specialized transduction would include
 

15)
 

______

 

  1. A)

 

the cos site.
 

  1. B)

 

the att region.

 

  1. C)

 

a helper phage.
 

  1. D)

 

all of the above.

 

 

 

16)
 

Lysogeny probably carries a strong selective advantage for the host cell because
 

16)
 

______

 

  1. A)

 

it confers resistance to infection by viruses of a different type (or strain).

 

  1. B)

 

it prevents cell lysis.

 

  1. C)

 

it confers resistance to infection by viruses of the same type.

 

  1. D)

 

of all of the above.

 

 

 

17)
 

A plasmid may
 

17)
 

______

 

  1. A)

 

replicate independently of the chromosome.

 

  1. B)

 

be integrated into the chromosome.

 

  1. C)

 

be transferred cell to cell during conjugation.

 

  1. D)

 

be involved in any of the above.

 

 

 

18)
 

Plasmids that govern their own transfer are known as
 

18)
 

______

 

  1. A)

 

transformable.
 

  1. B)

 

transfective.
 

  1. C)

 

transmutable.
 

  1. D)

 

conjugative.

 

 

 

19)
 

Which of the following would NOT be a trait of a resistance plasmid?
 

19)
 

______

 

  1. A)

 

It increases the host’s growth rate.

 

  1. B)

 

It may undergo genetic recombination.

 

  1. C)

 

It may carry heavy metal resistance genes.

 

  1. D)

 

It may carry antibiotic resistance genes.

 

 

 

20)
 

Homologous recombination has been observed in
 

20)
 

______

 

  1. A)

 

Bacteria.
 

  1. B)

 

Eukarya.

 

  1. C)

 

Archaea.
 

  1. D)

 

all of the above.

 

 

 

21)
 

Hfr strains of Escherichia coli


21)
 

______

 

  1. A)

 

do not possess an F factor.

 

  1. B)

 

have an integrated F factor.

 

  1. C)

 

transfer the complete F factor to recipient cells at a high frequency.

 

  1. D)

 

have the F factor as a plasmid.

 

 

 

22)
 

F+ strains of Escherichia coli


22)
 

______

 

  1. A)

 

do not have an F factor.

 

  1. B)

 

transfer the F factor to recipient cells at a high frequency.

 

  1. C)

 

have an integrated F factor.

 

  1. D)

 

have the F factor as a plasmid.

 

 

 

23)
 

F- strains of Escherichia coli


23)
 

______

 

  1. A)

 

have an integrated F factor.

 

  1. B)

 

transfer the F factor to other strains at a high frequency.

 

  1. C)

 

do not have an F factor.

 

  1. D)

 

have the F factor as a plasmid.

 

 

 

24)
 

All Hfr strains integrate into the chromosome at
 

24)
 

______

 

  1. A)

 

the same locus most of the time, although there may be some variation.

 

  1. B)

 

the same locus.

 

  1. C)

 

several specific sites.

 

  1. D)

 

loci that cannot be accurately determined.

 

 

 

25)
 

Transposition is a(n)
 

25)
 

______

 

  1. A)

 

general recombination event.
 

  1. B)

 

homologous recombination event.

 

  1. C)

 

analogous recombination event.
 

  1. D)

 

site-specific recombination event.

 

 

 

26)
 

The enzyme transposase may be coded for by (the)
 

26)
 

______

 

  1. A)

 

IS on a phage.
 

  1. B)

 

IS on a plasmid.

 

  1. C)

 

IS on a chromosome.
 

  1. D)

 

all of the above.

 

 

 

27)
 

A strain of an organism with an increased mutation rate is known as a(n)
 

27)
 

______

 

  1. A)

 

hypermutable or mutator strain.
 

  1. B)

 

encoded dnaQ system.

 

  1. C)

 

adaptive mutagen strain.
 

  1. D)

 

phenotypic variation.

 

 

 

28)
 

A “point mutation” refers to mutations involving
 

28)
 

______

 

  1. A)

 

the gain of a base pair (microinsertion).

 

  1. B)

 

the deletion of a base pair (microdeletion).

 

  1. C)

 

a base-pair substitution.

 

  1. D)

 

any of the above.

 

 

 

29)
 

A mutation in recA results in
 

29)
 

______

 

  1. A)

 

a decrease in homologous recombination.

 

  1. B)

 

an increase in homologous recombination.

 

  1. C)

 

a decrease in specific recombination.

 

  1. D)

 

no change in either general or specific recombination.

 

 

 

30)
 

The production of a functional gene product by transforming bacteria that lack a lacZ gene with a plasmid containing a lacZ gene is known as
 

30)
 

______

 

  1. A)

 

conjugation.
 

  1. B)

 

transfection.

 

  1. C)

 

cis complementation.
 

  1. D)

 

trans complementation.

 

 

 

31)
 

Consider conjugation in Escherichia coli. In which of the following matings would chromosomal genes be transferred most frequently?
 

31)
 

______

 

  1. A)

 

F- × F-
 

  1. B)

 

Hfr × F+
 

  1. C)

 

F+ × F-
 

  1. D)

 

Hfr × F-

 

 

 

32)
 

Which of the following features are common to transformation, transduction, and conjugation?

(1) unidirectional transfer of genes

(2) incomplete gene transfer

(3) homologous recombination

(4) meiosis occurring in the recipient
 

32)
 

______

 

  1. A)

 

1, 2, 3
 

  1. B)

 

1, 2, 4
 

  1. C)

 

1, 2
 

  1. D)

 

3, 4

 

 

 

33)
 

Which of the following is most similar to lysogeny?
 

33)
 

______

 

  1. A)

 

F+ state
 

  1. B)

 

Hfr state
 

  1. C)

 

F- state
 

  1. D)

 

F’ state

 

 

 

34)
 

In the bacterial world, a gene located on which of the following would be the LEAST likely to be transferred?
 

34)
 

______

 

  1. A)

 

the chromosome
 

  1. B)

 

R factor

 

  1. C)

 

the phage Mu
 

  1. D)

 

F+

 

 

 

35)
 

Genetic recombination involving insertion sequences typically results in what type of mutation?
 

35)
 

______

 

  1. A)

 

base-pair substitution mutation
 

  1. B)

 

silent mutation

 

  1. C)

 

missense mutation
 

  1. D)

 

frameshift mutation

 

 

 

36)
 

The SOS regulatory system is activated by
 

36)
 

______

 

  1. A)

 

the activity of DNA polymerase IV.
 

  1. B)

 

repression of RecA.

 

  1. C)

 

transcription of LexA.
 

  1. D)

 

DNA damage.

 

 

 

37)
 

Frederick Griffith’s experiments, which showed that the R strain was able to pick up DNA from a heat-treated S strain of Streptococcus pneumonia, provided the first evidence of
 

37)
 

______

 

  1. A)

 

conjugation.
 

  1. B)

 

transformation.

 

  1. C)

 

homologous recombination.
 

  1. D)

 

transduction.

 

 

 

38)
 

Transformation and homologous recombination allow for the formation of heteroduplex DNA. Which of the following would occur during DNA replication of this molecule?
 

38)
 

______

 

  1. A)

 

Both daughter strands are complementary to the recombinant DNA molecule.

 

  1. B)

 

One daughter strand is complementary to the recombinant DNA molecule, while the other daughter strand is complementary to the parent DNA molecule.

 

  1. C)

 

Both daughter strands are complementary to the parent DNA molecule.

 

  1. D)

 

None of the above is correct.

 

 

 

39)
 

A transducing particle is produced during the type of genetic recombination known as
 

39)
 

______

 

  1. A)

 

transformation.
 

  1. B)

 

generalized transduction.

 

  1. C)

 

conjugation.
 

  1. D)

 

specialized transduction.

 

 

 

40)
 

Which is a phenotype of an F- cell?
 

40)
 

______

 

  1. A)

 

The cell can synthesize an F pilus.

 

  1. B)

 

The cell can participate as a donor in conjugation.

 

  1. C)

 

The cell can take up DNA from an F-containing donor cell.

 

  1. D)

 

The chromosomal DNA can be transferred to another cell.

 

 

 

TRUE/FALSE.  Write ‘T’ if the statement is true and ‘F’ if the statement is false.


41)
 

UV radiation is a useful tool in producing mutants of microbial cultures.
 

41)
 

______

 

 

 

42)
 

When UV radiation damage occurs, DNA repair occurs only in the absence of template instruction.
 

42)
 

______

 

 

 

43)
 

Following uptake, transforming DNA becomes attached to a competence-specific protein that prevents it from nuclease attack until it reaches the chromosome.
 

43)
 

______

 

 

 

44)
 

The evolutionary significance of phage conversion likely stems from an effective alteration of host cells.
 

44)
 

______

 

 

 

45)
 

Bacterial mating (or conjugation) is a bidirectional process where nucleic acids (DNA or RNA) are transferred during a cell-to-cell interaction involving a donor and a recipient cell.
 

45)
 

______

 

 

 

46)
 

The F plasmid of Escherichia coli is about 99 kbp and is present in both F+ and F- strains.
 

46)
 

______

 

 

 

47)
 

Almost all plasmids are double-stranded DNA.
 

47)
 

______

 

 

 

48)
 

Most plasmids are circular rather than linear.
 

48)
 

______

 

 

 

49)
 

When the F factor is integrated, all Hfr strains have the origin of replication functioning in the same direction.
 

49)
 

______

 

 

 

50)
 

The IS element cannot code for the transposase enzyme.
 

50)
 

______

 

 

 

51)
 

The use of transposons to generate mutations is a convenient way to create bacterial mutations in the laboratory.
 

51)
 

______

 

 

 

52)
 

Of the transposons that are now widely used, Tn5 and Tn10 carry antibiotic resistance markers to select for mutants.
 

52)
 

______

 

 

 

53)
 

In transformation experiments using a variety of Bacteria, it has been noted that essentially all of the cells in a population can become competent.
 

53)
 

______

 

 

 

54)
 

In generalized transduction, virtually any genetic marker can be transferred from donor to recipient at a high frequency. This process may occur with either a temperate or a virulent phage.
 

54)
 

______

 

 

 

55)
 

In specialized transduction, as exemplified in the lambda-Gal system, transduction by a lysate occurs at high efficiency for only a restricted group of gal genes, and induction of a lysogenic cell is required.
 

55)
 

______

 

 

 

56)
 

Many Bacteria isolated from nature are natural lysogens.
 

56)
 

______

 

 

 

57)
 

It is likely that lysogeny has a selective advantage in nature.
 

57)
 

______

 

 

 

58)
 

Proteins and nucleic acids absorb light maximally at 260 nm; hence, proteins protect cells from UV effects.
 

58)
 

______

 

 

 

59)
 

ISs do not encode for known phenotypic traits and are smaller than either Tn or Mu.
 

59)
 

______

 

 

 

60)
 

Toxigenicity in Corynebacterium diphtheriae is due to phase conversion (lysogenization with β phage).
 

60)
 

______

 

 

 

61)
 

All Hfr strains possess an F factor integrated into the host chromosome.
 

61)
 

______

 

 

 

62)
 

Penicillin selection is a positive selection for the isolation of mutants with growth factor requirements.
 

62)
 

______

 

 

 

63)
 

Intercalating agents, like acridine orange and ethidium bromide, lead to mutagenesis by pushing DNA base pairs apart, which can lead to insertions or deletions.
 

63)
 

______

 

 

 

64)
 

A typical mutation rate for a bacterium is in the range of 10-6 to 10-9 per kbp.
 

64)
 

______

 

 

 

65)
 

Archaea contain a conjugation mechanisms similar to Bacteria, but they also have a unique form involving cytoplasmic bridges for bidirectional transfer of DNA.
 

65)
 

______

 

 

 

SHORT ANSWER.  Write the word or phrase that best completes each statement or answers the question.


66)
 

Hfr means ________, and these cells are capable of transferring genes from their ________.
 

66)
 

_____________

 

 

 

67)
 

A mutation that replaces a pyrimidine with another pyrimidine or a purine with another purine is called a(n) ________, and a(n) ________ is a mutation of a purine to a pyrimidine or a pyrimidine to a purine.
 

67)
 

_____________

 

 

 

68)
 

The appropriate designation for the phenotype of a histidine-requiring strain of Escherichia coli would be ________.
 

68)
 

_____________

 

 

 

69)
 

A(n) ________ is a set of genes or operons that are all under the control of a particular type of ________ .
 

69)
 

_____________

 

 

 

70)
 

Microinsertions and microdeletions often result in ________ mutations.
 

70)
 

_____________

 

 

 

71)
 

A cellular mechanism, known as the ________, is activated because of DNA damage and initiates a number of DNA repair processes.
 

71)
 

_____________

 

 

 

72)
 

The F (fertility) plasmid contains a set of genes that  encode for the ________ proteins that are essential in conjugative transfer of DNA.
 

72)
 

_____________

 

 

 

73)
 

The designations Phe-, Leu-, and Ser+ refer to an organism’s ________.
 

73)
 

_____________

 

 

 

74)
 

If a bacterium carrying a plasmid that confers resistance to ampicillin is placed into medium without ampicillin, the loss of the plasmid is a phenomenon known as ________.
 

74)
 

_____________

 

 

 

75)
 

One method of determining the order in which genes are present on an Hfr donor is to perform a kinetics experiment involving ________ of conjugating cells.
 

75)
 

_____________

 

 

 

76)
 

Called “crossing over” in classical genetics, the process in which DNA sequences are exchanged is now more commonly termed ________.
 

76)
 

_____________

 

 

 

77)
 

________ is a specific type of transformation where bacteriophage DNA is taken up by bacterial cells.
 

77)
 

_____________

 

 

 

78)
 

________ when a bacterium’s phenotype changes as the result of a(n) ________ into its genome.
 

78)
 

_____________

 

 

 

79)
 

A bacterium containing two copies of a chromosomal nucleotide sequence is called a(n) ________. Typically one copy is present on the ________ and the other on a(n) ________.
 

79)
 

_____________

 

 

 

80)
 

The two primary mechanisms of transposition are ________ and ________.
 

80)
 

_____________

 

 

 

ESSAY.  Write your answer in the space provided or on a separate sheet of paper.


81)
 

Name and describe a test that could be performed to determine if a kitchen chemical cleaner is mutagenic. Also mention the purpose of control(s) for the test and how the results are interpreted.

 

 

 

82)
 

Explain how electroporation works and the outcome of the procedure.

 

 

 

83)
 

Compare and contrast generalized transduction with specialized transduction.

 

 

 

84)
 

Use an example to describe the basis of the penicillin-selection method and why it is used.

 

 

 

85)
 

Discuss the similarities and differences between transposons and insertion sequence (IS) elements.

 

 

 

86)
 

Compare and contrast silent mutations, missense mutations, and nonsense mutations, including the effect each would have on a protein.

 

 

 

87)
 

Explain why HIV (an RNA virus) has a high mutation rate compared to a DNA genome.

 

 

 

88)
 

Explain why point mutations may occasionally revert, while large-scale deletions do not revert.

 

 

 

89)
 

Why might transposon mutagenesis be favored over chemical mutagenesis?

 

 

 

90)
 

How might mutations in the dnaQ sequence, whose enzyme is involved in DNA proofreading, be beneficial for a microbe in the environment?

 

 

 

1)
 

A

 

2)
 

B

 

3)
 

A

 

4)
 

D

 

5)
 

A

 

6)
 

A

 

7)
 

D

 

8)
 

D

 

9)
 

B

 

10)
 

D

 

11)
 

C

 

12)
 

A

 

13)
 

C

 

14)
 

B

 

15)
 

D

 

16)
 

C

 

17)
 

D

 

18)
 

D

 

19)
 

A

 

20)
 

D

 

21)
 

B

 

22)
 

D

 

23)
 

C

 

24)
 

C

 

25)
 

D

 

26)
 

D

 

27)
 

A

 

28)
 

D

 

29)
 

A

 

30)
 

D

 

31)
 

D

 

32)
 

A

 

33)
 

B

 

34)
 

A

 

35)
 

D

 

36)
 

D

 

37)
 

B

 

38)
 

B

 

39)
 

B

 

40)
 

C

 

41)
 

TRUE

 

42)
 

FALSE

 

43)
 

TRUE

 

44)
 

TRUE

 

45)
 

FALSE

 

46)
 

FALSE

 

47)
 

TRUE

 

48)
 

TRUE

 

49)
 

FALSE

 

50)
 

FALSE

 

51)
 

TRUE

 

52)
 

TRUE

 

53)
 

FALSE

 

54)
 

FALSE

 

55)
 

TRUE

 

56)
 

TRUE

 

57)
 

TRUE

 

58)
 

FALSE

 

59)
 

TRUE

 

60)
 

TRUE

 

61)
 

TRUE

 

62)
 

FALSE

 

63)
 

TRUE

 

64)
 

TRUE

 

65)
 

TRUE

 

66)
 

high frequency of recombination / chromosome

 

67)
 

transition / transversion

 

68)
 

His-

 

69)
 

regulon / regulatory protein

 

70)
 

frameshift

 

71)
 

SOS regulatory system

 

72)
 

F pili

 

73)
 

phenotype

 

74)
 

curing

 

75)
 

interrupted mating

 

76)
 

homologous recombination

 

77)
 

Transfection

 

78)
 

Phage conversion / bacteriophage

 

79)
 

merodiploid / chromosome / plasmid

 

80)
 

conservative / replicative (either order)

 

81)
 

The Ames test could be used to determine if the cleaner solution causes mutations in bacteria. An auxotrophic mutant strain (e.g., Salmonella enterica His-) containing a point mutation is most helpful for this test, so it can measurably revert in small populations of cells. A His- cell population exposed to various concentrations of the cleaner solution would then be put into agar plates lacking histidine, and the number of colonies that grew would represent cells that mutated back to wildtype (His+). An important control for the test is to plate an equal number of cells not exposed to the cleaner solution on to the same medium to calculate a baseline mutation rate of the cells when not exposed to the chemical cleaner. If there are significantly more His+ revertants that grew after exposure to the cleaner solution, then the chemical is mutagenic.

 

82)
 

Electroporation involves pulsing cells with a high voltage. The brief electrical charge makes cells temporarily permeable such that foreign DNA (e.g., plasmids) can be taken up. This process yields artificially constructed transformants and is a key step in genetic manipulation.

 

83)
 

Transduction as a whole is the transfer of genetic information from one cell to another mediated by a virus. Generalized transduction allows for the transfer of any portion of a cell’s genome to be transferred, but this process occurs at a very low frequency (roughly 10-6 to 10-8). Specialized transduction transfers only genetic material adjacent to the integrated phage (prophage), however its transfer efficiency is much higher than in generalized transduction.

 

84)
 

The antibiotic penicillin works only to kill cells that are actively replicating. Penicillin can be added to a medium lacking a particular amino acid (e.g., Trp) to negatively select for rare auxotrophic mutants (Trp-) of interest among a large population of Trp+ cells. The Trp- mutants will not grow in the absence of Trp supplemented media, and therefore only the Trp+ cells will be killed. After removing penicillin from the medium, Trp can be added to increase the population of Trp- auxotrophic mutants of interest.

 

85)
 

Both contain a transposase gene as well as inverted repeats at their termini. IS elements are smaller than transposons, usually having a length of 1 to 2.5 kbp. IS elements are also the simplest in that they contain only the nucleotide information required for transposition, whereas transposons also contain accessory genes such as antibiotic resistance.

 

86)
 

All three point mutations describe one change in the nucleotide sequence. Silent mutations can have slightly modified protein structures or unmodified ones, as long as the nucleotide change does not result in any change of the phenotype. Missense mutations are more restricted in that a nucleotide change results in a particular amino acid (codon) change. Although a missense mutation will change the amino acid sequence, this again may or may not change the structure of the protein. A nonsense mutation is the most specific of all where the nucleotide sequence now contains an inserted non-native stop site. The premature halt of protein synthesis will result in a shortened protein structure.

 

87)
 

DNA and RNA polymerases both make roughly the same number of errors during synthesis, but it is the proofreading mechanisms that greatly differ between DNA and RNA genomes. HIV does not have any system to repair these errors compared to organisms with DNA genomes, which often contain several.

 

88)
 

Because a point mutation involves only a single base pair change, reversion is quite common relative to fixing a deletion of several nucleotides. Common in Bacteria are suppressor mutations, which suppress the initial mutation and restore the wild-type phenotype (but not genotype) of a point mutation. However no analogous mechanism works to fix large-scale deletions.

 

89)
 

The use of transposons such as Tn5 and Tn10 is an excellent way to positively select for mutants using kanamycin or tetracycline (respectively) in a growth medium. This is very useful, especially when there is no other way to select for the newly generated mutants, because only the mutants containing the Tn-inserted antibiotic resistance marker will grow.

 

90)
 

These mutations in dnaQ would result in an increase in mutations; however unrepaired mutations are not always lethal. In this situation, mutagenesis might be thought of as creating diversity of a microbe’s genome. Genetic diversity might create a genotype different enough that a new phenotype arises. If for example the new phenotype is an ability to catabolize a particular compound, this could provide the cell with the ability to survive using a different substrate for energy when others are limited. Also, if a certain cell surface component is the target for phage infection and lysis, a different gene sequence could modify the surface component to perhaps enhance survivability in the environment.

Brock Biology of Microorganisms Michael T. Madigan 13th Edition Test Bank

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