Deck 16: Mechanisms of Genetic Variation

Question 1

Stable integration of foreign DNA into a bacterial host genome is generally accomplished through induced plasmid transformation than by natural uptake of free DNA fragments.

Answer 1

False

Question 2

The transformation frequency of very competent cells is about 10^-6,or about 1 in 1,000,000 when an excess of DNA is used.

Answer 2

False

Question 3

Which procedure is most associated with unsuccessful transformation and degradation of DNA?

A)Naturally-occurring transformation with DNA fragments in competent bacteria.
B)Induced transformation with plasmid DNA in noncompetent bacteria.
C)Integration of DNA fragments in competent bacteria following naturally-occurring transformation.
D)Addition of DNA fragments from competent bacteria to live,noncompetent bacteria without artificial induction.

Answer 3

A

Question 4

A microbiologist is working with two genera of bacteria,A and B,to determine if cells are competent.Strains are grown under optimal conditions,and DNA fragments that carry the gene for green fluorescent protein is added to each culture at 20-minute intervals.Samples from each treatment are plated to nutrient agar and incubated,after which the plates are examined under an ultraviolet lamp.The microbiologist observes that all plates of bacteria B contain colonies that are fluorescent,while for bacteria A only the plates from stationary phase demonstrate fluorescent colonies.What can be concluded from these results?

A)Both bacteria A and bacteria B cells are competent.
B)Competence in bacteria A is constitutively expressed.
C)Competence in bacteria B is dependent on the phase of growth.
D)Neither bacteria A nor bacteria B cells are competent.

Question 5

During specialized transduction carried out by lambda phage in Escherichia coli,differences in the phage and host attachment (att)sites mediate insertion of phage DNA into host DNA.

Question 6

A(n)__________ is a latent form of a virus genome that remains within the host without destroying it.

Question 7

In order to take up a naked DNA molecule,a cell must be __________,which may occur only at certain stages in the life cycle of the organism.

Question 8

If chromosomal DNA from a host is the only type of DNA carried by a transducing particle,what can be concluded regarding transduction in this case?

A)Transduction in this case is generalized rather than specialized.
B)Transduction in this case is specialized rather than generalized.
C)Transduction in this case could be generalized or specialized depending on the phage involved.
D)Transduction in this case is neither generalized nor specialized.

Question 9

A microbiologist is working with a bacteria strain to determine if cells are competent.Cells are grown under optimal conditions with DNA fragments that carry two genes,green fluorescent protein and ampicillin resistance,and then plated to nutrient agar with and without ampicillin.Following incubation,plates are examined for fluorescent colonies under a UV lamp.Predict the results if cells are competent.

A)Fluorescent colonies will be present on both types of plates.
B)Fluorescent colonies will be present on the the ampicillin agar plates,but there will be no growth on the nutrient agar plates.
C)Colonies will be present on both types of plates,but will only fluoresce on the ampicillin agar plates.
D)There will be no growth on either type of plate.

Question 10

Genes for antibiotic resistance can be found in antibiotic-producing bacteria as well as in non-antibiotic-producing bacteria.

Question 11

Which of the following is not true of specialized transduction?

A)It is carried out by temperate phage.
B)It is restricted to those genes on either side of an integrated prophage.
C)The phage genome retains the full complement of phage genes.
D)All of the choices are correct.

Question 12

Which of the following is not a strategy that bacteria use to resist the action of antibiotics?

A)Modification of the antibiotic by the acetylation or phosphorylation.
B)Cleavage of a key structural component of the antibiotic.
C)Altering cell membrane structure to prevent antibiotic influx.
D)All of the choices are correct.

Question 13

Specialized transduction can be carried out by

A)any bacteriophage.
B)any temperate bacteriophage.
C)only those temperate bacteriophages that integrate into the host chromosome.
D)All of the choices are correct.

Question 14

As pertaining to the spread of antibiotic resistance in bacteria,which of the following terms is not directly related to the others?

A)Intercalate
B)Cassette
C)Integron
D)Integrase

Question 15

All of the following are appropriate strategies for overcoming drug resistance in bacteria except

A)decreasing the use of antibiotics in agriculture.
B)patient compliance with dosage instructions when taking antibiotics.
C)heightened infection control in health care facilities.
D)prudent use of antibiotics when treating viral infections.

Question 16

If the att site of Escherichia coli was dissimilar to that of lambda phage due to a mutation,how would transduction be affected?

A)Phage DNA would be unable to integrate into host DNA.
B)Lambda phage would be unable to package host DNA.
C)Specialized transduction would become generalized.
D)Transduction would not be affected since mutation is only in the host cell.

Question 17

During generalized transduction

A)the host chromosome is degraded into randomly sized fragments.
B)any DNA fragment of the appropriate size is packaged.
C)any bacterial gene may be transferred to the subsequent host.
D)All of the choices are correct.

Question 18

One strategy to overcome antibiotic resistance is to use the same antibiotics in animal husbandry as those that are prescribed for humans,since the potential for resistant bacteria to evolve would be limited to only a small number of drug classes.

Question 19

If chromosomal DNA from a host and phage DNA are carried by a transducing particle,what can be concluded regarding transduction in this case?

A)Transduction in this case is generalized rather than specialized.
B)Transduction in this case is specialized rather than generalized.
C)Transduction in this case could be generalized or specialized depending on the phage involved.
D)Transduction in this case is neither generalized nor specialized.

Question 20

Transformation has been observed in only a limited number of species in nature,but we have found ways to force the process upon other species in the laboratory.

Question 21

Who is credited with demonstrating unidirectional and nonreciprocal transfer of DNA between two mating

A)Hayes
B)Lederberg
C)Tatum
D)None of the choices are correct.
E)coli cells?

Question 22

A plasmid that can either exist independently of the chromosome or be integrated into it is called a(n)__________.

Question 23

When assessing the role of conjugative bacteria in the spread of antibiotic resistance genes,it is fair to say that Hfr cells contribute most while F^- cells contribute least.

Question 24

A cell that is Hfr and a cell that is F⁺ can be the same cell.

Question 25

In the mechanics of conjugation,exclusive of gene transfer,Hfr and F⁺ strains behave the same.

Question 26

After an F⁺ * F^- mating,the donor is __________ and the recipient is __________.

A)F⁺; F^-
B)F^-; F⁺
C)F^-; F^-
D)F⁺; F⁺

Question 27

An Hfr cell and an F^- cell result from conjugation between a donor cell and a recipient cell.Which statement is false regarding this event?

A)The donor could have been either F^- or F⁺.
B)The donor could have been Hfr.
C)The recipient could have been F^-.
D)The donor could not have been F^-.

Question 28

In an HFR * F⁺ mating,the conjugation bridge usually breaks before chromosomal transfer is complete.Therefore,the recipient remains F^-.

Question 29

When an F' plasmid acts as the donor in a mating,which of the following do(es)not happen?

A)The recipient becomes F'.
B)The plasmid is transferred,including the chromosomal genes now on the plasmid.
C)Some chromosomal genes not on the plasmid are transferred.
D)All of the choices are correct.

Question 30

Complete transfer in an Hfr *F^- mating takes approximately __________ minutes.

A)20
B)50
C)100
D)200

Question 31

Predict the outcome of an F⁺ to F^- mating if the F⁺ cell lacked a functional tra operon.

A)Upon entering the recipient,the F factor would be unable to integrate into to host chromosome.
B)Conjugation would not occur because there would be no contact between the F⁺ and F^- cells.
C)Conjugation would occur,but the F^- recipient could not become Hfr.
D)There would be no effect on conjugation.

Question 32

A __________ is a piece of extrachromosomal DNA that has its own replication origin.

Question 33

Plasmids that have genes that decrease bacterial susceptibility to antibiotics are called __________ factors.

A)col
B)resistance
C)virulence
D)metabolic

Question 34

An F' plasmid results when

A)an F⁺ /F^- mating is interrupted before completion.
B)an Hfr * F^- mating is interrupted before completion.
C)an integrated F plasmid is incorrectly excised,bringing host genes with it.
D)None of the choices are correct.

Question 35

The conjugation bridge in an Hfr * F^- mating usually breaks before chromosome transfer is complete; however,because at least part of the plasmid is transferred first,the recipient becomes F⁺.

Question 36

The order of gene transfer in an Hfr * F^- mating is best represented by

A)all plasmid genes followed by some or all of the chromosome.
B)part of the plasmid followed by the chromosome followed by the rest of the plasmid.
C)the chromosome followed by the plasmid.
D)part of the chromosome followed by the plasmid followed by the rest of the chromosome.

Question 37

In an F⁺ * F^- conjugation,the donor is the __________ strain.

A)F⁺
B)F^-
C)both F⁺ and F^- (It is a reciprocal exchange)
D)neither F⁺ nor F^- (There is no exchange)

Question 38

Plasmids that have genes for pili and can transfer copies of themselves to other bacteria during conjugation are called __________ plasmids.

Question 39

When an F plasmid integrates into the host chromosome,the strain is referred to as

A)F⁺.
B)Hfr.
C)F'.
D)F^-.

Question 40

In an F⁺ *F^- mating,all or part of the host chromosome usually is transferred to the recipient.

Question 41

A transposable element composed of an antibiotic resistance gene,a recombinase gene,and inverted repeats is identified in a bacterial genome.This element can be any of the following except

A)an insertion sequence.
B)a composite transposon.
C)a unit transposon.
D)an integrated conjugative element.

Question 42

Which of the following effects may be mediated by transposable elements?

A)A mutation may result from insertion into a gene.
B)Activation of nearby genes may occur.
C)Genetic deletions may form.
D)All of the choices are correct.

Question 43

Which statement best summarizes the major distinction between horizontal gene transfer and vertical gene transfer?

A)The recipient of genes in horizontal transfer is a mature cell,whereas the recipient of genes in vertical transfer is a progeny cell.
B)Horizontal transfer is observed in bacteria and archaea,whereas vertical transfer is observed in all cells.
C)Organisms that use horizontal transfer can only reproduce asexually,whereas organisms that use vertical transfer can reproduce sexually or asexually.
D)Genes are more stable in recipient cells following horizontal transfer that in those following vertical transfer.

Question 44

If one reproductive strategy of a eukaryotic organism is gamete fusion,what can be concluded about that organism?

A)The organism participates in vertical gene transfer.
B)The organism participates in horizontal gene transfer.
C)The organism reproduces asexually.
D)Progeny organisms are identical to each other.

Question 45

Insertion sequences are

A)normally relatively short (700 to 1,650 bp).
B)capable of transposition.
C)are discrete genetic elements bounded at both ends with inverted repeats.
D)All of the choices are correct.

Question 46

Which of the following conclusions can be made if two identical insertion sequences are identified in separate locations on a chromosome?

A)The insertion sequence was transferred via replicative transposition.
B)The insertion sequence was a "cut-and-paste" transposon.
C)The insertion sequence was transferred via simple transposition.
D)A mutation occurred during transposition of the insertion sequence.

Question 47

A reciprocal exchange in which a pair of DNA with the same nucleotide sequence break and rejoin in a crossover is called __________ recombination.

A)homologous
B)site-specific
C)replicative
D)None of the choices are correct.

Question 48

An insertion sequence is distinguishable from other mobile genetic elements because

A)it is smallest.
B)it encodes a transposase.
C)it is highly complex.
D)it is composed of DNA.

Question 49

A DNA molecule that enters a bacterium by one of several mechanisms is called a(n)

A)merozygote.
B)exogenote.
C)endogenote.
D)None of the choices are correct.

Question 50

Which of these transposable elements do not carry genes for functions other than those needed for transposition?

A)Insertion sequences
B)Composite transposons
C)Retrotransposons
D)Conjugal transposons

Question 51

Which of the following methods of genetic recombination is common to both eukaryotic and bacterial cells?

A)Vertical gene transfer
B)Crossing over
C)Gamete fusion
D)All of the choices are correct.

Question 52

The genome of a recipient cell is called a(n)__________.

A)merozygote
B)exogenote
C)endogenote
D)None of the choices are correct.

Question 53

The process in which one or more nucleic acid molecules are rearranged or combined to produce a new nucleotide sequence is called

A)transformation.
B)conjugation.
C)recombination.
D)transduction.

Question 54

Transposons that insert at a new location while a copy remains at the original location are said to mediate _______________ transposition.

A)simple
B)composite
C)incomplete
D)replicative

Question 55

When a recipient cell acquires a piece of naked DNA from the environment,it is called

A)conjugation.
B)transformation.
C)transduction.
D)transfection.

Question 56

Bacterial isolates from post surgical infections of several patients on the same hospital floor demonstrate an increase in resistance to similar antibiotics.The pattern of antibiotic resistance in these cases is most likely due to vertical gene transfer among bacteria that carry resistance genes to bacteria that lack those genes.

Question 57

The incorporation of a single strand of donor DNA into a recipient DNA duplex so that the donor strand replaces one of the strands or the recipient duplex generates __________ DNA.

A)aberrant
B)unstable
C)heterogeneous
D)heteroduplex

Question 58

Transposable elements have been found only in prokaryotes and do not appear to play a major role in eukaryotes.

Question 59

Site-specific recombination systems

A)do not depend on extensive nucleotide sequence homology.
B)depend on enzymes that are often specific for sequences within the host.
C)are features of some viruses.
D)All of the choices are correct.

Question 60

Conjugative transposons

A)can be transferred from one bacterium to another by a phage mediated process.
B)may be involved in the spread of antibiotic resistance in bacteria.
C)often express enzymes that degrade aromatic compounds.
D)All of the choices are correct.

Question 61

Microbial strains that can grow on minimal medium are called __________.

A)autotrophs
B)auxotrophs
C)prototrophs
D)minitrophs

Question 62

To best isolate mutant bacteria that are threonine auxotrophs from a larger population,threonine-rich media should be inoculated and any colonies that form are presumptive auxotrophic mutants.

Question 63

A public health microbiologist plans to screen a particular bacterial species that was isolated from several patients in an intensive care unit to detect if any of the cells are penicillin-resistant mutants.What is the first step in conducting this experiment?

A)Determine whether or not wild type cells of the same bacterial species are susceptible to penicillin.
B)Test the cells to see if they can grow on media to which penicillin has been added.
C)Perform an antibiotic susceptibility test on the cells using antibiotics other than penicillin that are known to be effective.
D)Set up an Ames test to see if any of the isolates are mutagenic.

Question 64

SOS repair

A)requires RecA protein.
B)is inducible by DNA damage.
C)is error prone,i.e.,produces mutations.
D)All of the choices are correct.

Question 65

In mismatch repair on newly replicated DNA,enzymes distinguish between old and newly replicated DNA strands based on the fact that newly replicated DNA strands are ________-methylated relative to older DNA.
or

Question 66

One possible fate for an exogenote is

A)integration into the host chromosome.
B)independent replication and functioning.
C)degradation to nucleotides.
D)All of the choices are correct.

Question 67

What would be the hypothetical outcome if the action of RecA were inhibited during the SOS response?

A)LexA would not autolyse,and therefore the transcription of DNA repair genes would not occur.
B)LexA would autolyse,and therefore the transcription of DNA repair genes would occur.
C)LexA would autolyse,and therefore the transcription of repair genes would not occur.
D)LexA would not autolyse,and therefore the transcription of repair genes would occur.

Question 68

Repair of thymine dimers using light to split the dimers apart into separate monomers is called

A)photodedimerication.
B)photoreactivation.
C)photoreparation.
D)None of the choices are correct.

Question 69

Photoreactivation repairs thymine dimers by splitting them back into separate thymines.

Question 70

Which type of medium support growth of mutant bacteria that are threonine auxotrophs?

A)Threonine auxotrophs only grow on media that is supplemented with threonine.
B)Threonine auxotrophs only grow on media that lacks threonine.
C)Since threonine is essential for growth,threonine auxotrophs do not grow on any type of media.
D)Since threonine is essential for growth,threonine auxotrophs can grow on any type of media.

Question 71

A recipient cell that is temporarily diploid for a portion of the genome during the replacement process is called a(n)__________.

A)merozygote
B)exogenote
C)endogenote
D)None of the choices are correct.

Question 72

Host __________ is the process by which some cells are capable of degrading an exogenote.

Question 73

Which of the following is true of the integration of a viral genome into the host chromosome?

A)Integration of the viral genome is a form of site-specific recombination.
B)The enzymes that are used in integration are nonspecific for the virus and its host.
C)Integration begins the process of host chromosome degradation.
D)All of the choices are correct.

Question 74

If you wished to study the SOS response in Escherichia coli,which of the following experimental procedures could be used?

A)All of the choices are correct.
B)Expose cells to nonionizing radiation for 20 minutes.
C)Expose cells to ionizing radiation for 10 minutes.
D)Transfer log phase cells from complete medium to thymine minimal medium.
E)Inactivate genes that encode DNA polymerases.

Question 75

Repair of an apurinic or apyrimidinic site in DNA by AP endonuclease must be completed by the action of

A)UvrABC endonuclease.
B)RecA protein.
C)DNA polymerase I.
D)None of the choices are correct.

Question 76

Which type(s)of mutation might lead to a threonine auxotrophic revertant?

A)All of the choices are correct.
B)Base substitution
C)Missense mutation
D)Point mutation

Question 77

Which of the following is the most error-prone of the repair mechanisms?

A)Postreplication repair
B)Recombination repair
C)SOS repair
D)Photoreactivation

Question 78

What type of procedure is appropriate to isolate revertants from a population of threonine auxotrophic cells?

A)Grow the auxotrophic cells on an agar plate without threonine; any colonies that form are presumed revertant.
B)Grow the auxotrophic cells on and agar plate with threonine; any colonies that form are presumed revertant.
C)Grow the auxotrophic cells in broth with threonine; if the broth becomes cloudy,revertants are presumed present.
D)Threonine auxotrophic revertants could not be isolated on any type of media.

Question 79

When bacterial genes are transferred to another bacterium by a virus,it is called

A)conjugation.
B)transformation.
C)transduction.
D)transfection.

Question 80

Transfer of genes from one mature independent organism to another is called

A)horizontal gene transfer.
B)lateral gene transfer.
C)vertical gene transfer.
D)orthogonal gene transfer.