| A mutant that has a nutritional requirement for growth is an example of a(n)
A) autotroph.
B) auxotroph.
C) heterotroph.
D) organotroph. | B) auxotroph. |
| 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?
A) silent mutation
B) nonsense mutation
C) missense mutation
D) frameshift mutation | A) silent mutation |
| A mutation that readily reverses to restore the original parental type would most likely be due to a(n)
A) deletion.
B) insertion.
C) point mutation.
D) frameshift mutation. | C) point mutation. |
| Which process listed below does NOT require homologous recombination to maintain the new genetic material in the recipient cell?
A) conjugation of an F+ plasmid
B) gene transfer through a genetic transfer agent
C) transduction by a dsDNA phage Mu
D) transformation of a linear piece of DNA | B) gene transfer through a genetic transfer agent |
| The mutagens 2-aminopurine and 5-bromouracil are examples of
A) alkylating agents.
B) nucleotide base analogs.
C) chemicals reacting with DNA.
D) None of the answers are correct. | B) nucleotide base analogs. |
| The killing of cells by UV irradiation involves
A) absorption at 260 nm by proteins only.
B) absorption at 260 nm by RNA only.
C) formation of pyrimidine dimers.
D) formation of purine dimers. | C) formation of pyrimidine dimers. |
| Ionizing radiation does NOT include
A) gamma rays.
B) UV rays.
C) X-rays.
D) cosmic rays. | B) UV rays. |
| Which of the following methods may introduce foreign DNA into a recipient?
A) transformation
B) transduction
C) conjugation
D) transformation, transduction, and conjugation | D) transformation, transduction, and conjugation |
| The uptake of DNA released from a cell is ________, while transfer of DNA with cell-to-cell contact would most likely result in ________.
A) transformation / conjugation
B) transduction / conjugation
C) conjugation / transformation
D) transformation / transduction | A) transformation / conjugation |
| Which of the following proteins is NOT required for homologous recombination?
A) Hfr
B) RecA
C) proteins having helicase activity
D) endonuclease | A) Hfr |
| 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?
A) The colonies may be due to back mutation (reversion).
B) The colonies may be due to recombination.
C) Either A or B is possible.
D) Neither A nor B is possible. | C) Either A or B is possible. |
| 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?
A) minimal medium
B) minimal medium + streptomycin
C) minimal medium + threonine
D) minimal medium + streptomycin + threonine | B) minimal medium + streptomycin |
| Horizontal gene transfer in Archaea
A) is infrequent in nature and therefore difficult to use for genetic studies in the laboratory.
B) has not been documented, thus all genetic studies of archaea are done via genomic sequencing.
C) frequently occurs in nature and has been used to perform genetic studies in the laboratory as well.
D) frequently occurs in nature, but there are very few laboratory studies because archaea do not cause human disease. | C) frequently occurs in nature and has been used to perform genetic studies in the laboratory as well. |
| The positions of genes on a genetic map are marked according to
A) degrees.
B) nanometers.
C) radians.
D) minutes. | D) minutes. |
| The minimal amount of genetic information required for specialized transduction would include
A) the att region.
B) the cos site.
C) a helper phage.
D) the att region, cos site, and a helper phage. | D) the att region, cos site, and a helper phage. |
| Lysogeny probably carries a strong selective advantage for the host cell because it
A) prevents cell lysis.
B) confers resistance to infection by viruses of the same type.
C) confers resistance to infection by viruses of a different type (or strain).
D) confers resistance to infection by many virus types and prevent cell lysis. | B) confers resistance to infection by viruses of the same type. |
| A plasmid may
A) replicate independently of the chromosome.
B) be transferred cell-to-cell during conjugation.
C) be integrated into the chromosome.
D) replicate independently of the chromosome, integrate into the chromosome, or be transferred cell-to-cell during conjugation. | D) replicate independently of the chromosome, integrate into the chromosome, or be transferred cell-to-cell during conjugation. |
| Plasmids that govern their own transfer are known as
A) transformable.
B) transmutable.
C) conjugative.
D) transfective. | C) conjugative. |
| Which of the following would NOT be a trait of a resistance plasmid?
A) It may carry antibiotic resistance genes.
B) It may carry heavy metal resistance genes.
C) It increases the host's growth rate.
D) It may undergo genetic recombination. | C) It increases the host's growth rate. |
| Homologous recombination has been observed in
A) Archaea.
B) Bacteria.
C) Eukarya.
D) Archaea, Bacteria, and Eukarya. | D) Archaea, Bacteria, and Eukarya. |
| Hfr strains of Escherichia coli
A) do not possess an F factor.
B) have the F factor as a plasmid.
C) have an integrated F factor.
D) transfer the complete F factor to recipient cells at a high frequency. | C) have an integrated F factor. |
| F+ strains of Escherichia coli
A) do not have an F factor.
B) have the F factor as a plasmid.
C) have an integrated F factor.
D) transfer the F factor to recipient cells at a high frequency.
Answer: B | B) have the F factor as a plasmid. |
| F- strains of Escherichia coli
A) do not have an F factor.
B) have the F factor as a plasmid.
C) have an integrated F factor.
D) transfer the F factor to other strains at a high frequency. | A) do not have an F factor. |
| All Hfr strains integrate into the chromosome at
A) the same locus.
B) several specific sites.
C) the same locus most of the time, although there may be some variation.
D) loci that cannot be accurately determined. | B) several specific sites. |
| Transposition is a(n)
A) homologous recombination event.
B) analogous recombination event.
C) site-specific recombination event.
D) general recombination event. | C) site-specific recombination event. |
| The enzyme transposase may be coded for by insertion sequences on a
A) chromosome.
B) phage.
C) plasmid.
D) chromosome, phage, or plasmid. | D) chromosome, phage, or plasmid. |
| A strain of an organism with an increased mutation rate is known as a(n)
A) adaptive mutagen strain.
B) hypermutable or mutator strain.
C) encoded dnaQ system.
D) phenotypic variation. | B) hypermutable or mutator strain. |
| A "point mutation" refers to mutations involving
A) a base-pair substitution.
B) the gain of a base pair (microinsertion).
C) the deletion of a base pair (microdeletion).
D) a substitution, deletion, or addition of one base-pair. | D) a substitution, deletion, or addition of one base-pair. |
| A deleterious mutation in recA results in
A) a decrease in specific recombination.
B) a decrease in homologous recombination.
C) an increase in homologous recombination.
D) no change in either general or specific recombination. | B) a decrease in homologous recombination. |
| 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
A) complementation.
B) mitosis.
C) transfection.
D) reversion. | A) complementation. |
| Consider conjugation in Escherichia coli. In which of the following matings would chromosomal genes be transferred most frequently?
A) F+ × F-
B) F- × F-
C) Hfr × F-
D) Hfr × F+ | C) Hfr × F- |
| 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
A) 1, 2, 3
B) 1, 2
C) 3, 4
D) 1, 2, 4 | A) 1, 2, 3 |
| Which of the following is most similar to lysogeny?
A) Hfr state
B) F+ state
C) F- state
D) F' state | A) Hfr state |
| In the bacterial world, a gene located on which of the following would be the LEAST likely to be transferred?
A) R factor
B) F+
C) the phage Mu
D) the chromosome | D) the chromosome |
| Genetic recombination involving insertion sequences typically results in what type of mutation?
A) base-pair substitution mutation
B) silent mutation
C) frameshift mutation
D) base-pair deletion mutation | C) frameshift mutation |
| The SOS regulatory system is activated by
A) the activity of DNA polymerase IV.
B) DNA damage.
C) transcription of LexA.
D) repression of RecA. | B) DNA damage. |
| Which of the following factors has delayed the development of laboratory-based genetic systems in Archaea?
A) There are no documented systems of conjugation in Archaea.
B) Homologous recombination does NOT occur in Archaea.
C) Archaea do NOT host viruses or plasmids.
D) Many archaea grow in extreme or unusual conditions that make the use of agar and traditional mutant screening techniques problematic. | D) Many archaea grow in extreme or unusual conditions that make the use of agar and traditional mutant screening techniques problematic. |
| Transformation and homologous recombination allow for the formation of heteroduplex DNA. Which of the following would occur during DNA replication of this molecule?
A) One daughter strand is complementary to the recombinant DNA molecule, while the other daughter strand is complementary to the parent DNA molecule.
B) Both daughter strands are complementary to the recombinant DNA molecule.
C) Both daughter strands are complementary to the parent DNA molecule.
D) None of the answers are correct. | A) One daughter strand is complementary to the recombinant DNA molecule, while the other daughter strand is complementary to the parent DNA molecule. |
| You work for a biotechnology company that uses Streptomyces strains to produce pharmaceutical products. A phage has infected and killed some of your Streptomyces strains during production, resulting in dramatically decreased yields. To protect the strains from infection you propose to
A) introduce gene transfer agents into the Streptomyces cultures to transfer antibiotic resistance genes into your Streptomyces strains.
B) design and insert CRISPR spacer sequences into the genomes of your strains that are complementary to the genomes of the phages that are infecting the cultures.
C) infect the Streptomyces strains with a helper phage that will help the strains resist infection.
D) transform the Streptomyces strains with plasmids encoding antibody proteins that will protect them from phage infection. | B) design and insert CRISPR spacer sequences into the genomes of your strains that are complementary to the genomes of the phages that are infecting the cultures. |
| Hfr means high frequency of ________, and these cells are capable of transferring genes from their ________ to other cells.
A) transformation / chromosome
B) transduction / plasmids
C) recombination / chromosome
D) transduction / chromosome | C) recombination / chromosome |
| Mutation rates are similar in Bacteria and Archaea, yet certain stressful conditions mutation rates increase. Why is the mutation rate not constant and close to zero all of the time?
A) Increased mutation rates can be advantageous in rapidly changing environments because some random mutations may be useful for survival.
B) Microorganisms carefully control the mutation rate of their DNA to match the environmental conditions and maximize evolution.
C) The increased mutation rate under stressful conditions is an indication that the microorganisms can no longer replicate their DNA properly and are about to die.
D) Constant mutation rates would halt evolution completely. | A) Increased mutation rates can be advantageous in rapidly changing environments because some random mutations may be useful for survival. |
| Chemical mutagens, UV radiation, and ionizing radiation all increase mutation rates, but they have different mechanisms. Which type of mutagen would be best suited for creating large deletions and rearrangements within a genome?
A) chemical mutagens
B) UV radiation
C) ionizing radiation
D) Chemical, UV, and ionizing radiation would create large deletions and rearrangements if used in a very high dose. | C) ionizing radiation |
| ) The SOS system repairs DNA that has gaps, breaks, and other lesions by
A) cutting DNA from other parts of the genome and pasting it into the gaps or damaged areas.
B) stabilizing single-stranded DNA until the next round of normal replication.
C) using specialized DNA polymerases that will synthesize a new DNA strand even if there is not a normal complementary DNA strand to act as a template.
D) using available mRNA and a special RNA-dependent DNA polymerase to fill in the gaps and replace damaged DNA. | C) using specialized DNA polymerases that will synthesize a new DNA strand even if there is not a normal complementary DNA strand to act as a template. |
| Microinsertions and microdeletions often result in ________ mutations.
A) auxotrophic
B) advantageous
C) silent
D) frameshift | D) frameshift |
| When damaged or single-stranded DNA activates the RecA protein, the RecA protein stimulates the cleavage of LexA. This results in
A) repression of polymerase V and activation of endonuclease.
B) activation of the Hfr system.
C) derepression of the SOS system.
D) increased transduction and recombination. | C) derepression of the SOS system. |
| The F (fertility) plasmid contains a set of genes that encode for the ________ proteins that are essential in conjugative transfer of DNA.
A) pili
B) SOS repair
C) transduction
D) transformation | A) pili |
| The designations Phe-, Leu-, and Ser+ refer to an organism's
A) plasmid type.
B) genotype.
C) phenotype.
D) mutation type. | C) phenotype. |
| If a bacterium carrying a plasmid that confers resistance to ampicillin is placed into medium without ampicillin, it may
A) gain resistance to other antibiotics.
B) transfer resistance to other cultures in the laboratory.
C) undergo a reversion mutation.
D) lose the plasmid because there is no selection for ampicillin resistance. | D) lose the plasmid because there is no selection for ampicillin resistance. |
| When DNA is transferred into a prokaryotic cell it may
A) be degraded by enzymes.
B) replicate independent of the host chromosome.
C) recombine with the host chromosome.
D) be degraded by enzymes, replicate independent of the host chromosome, or recombine with the host chromosome. | D) be degraded by enzymes, replicate independent of the host chromosome, or recombine with the host chromosome. |
| The process in which related DNA sequences from two different sources are exchanged is called
A) transduction.
B) phage conversion.
C) reversion.
D) homologous recombination. | D) homologous recombination. |
| Integration of linear transforming DNA into the chromosome
A) is not required for the expression for the transformed genes.
B) is catalyzed by the RecA gene.
C) almost never occurs because restriction endonuclease will degrade the DNA before it is integrated.
D) only occurs in laboratory-based systems in artificial competent cells. | B) is catalyzed by the RecA gene. |
| High-efficiency natural transformation
A) is common in Bacteria and Archaea.
B) requires specialized DNA uptake, DNA binding, and integration proteins.
C) is only common in Archaea.
D) usually involves plasmids. | B) requires specialized DNA uptake, DNA binding, and integration proteins. |
| The CRISPR system
A) facilitates homologous recombination through a complex system of proteins and clustered repeats.
B) recognizes foreign DNA sequences that have previously entered the cell and directs the Cas proteins to destroy them.
C) repairs DNA and increases DNA damage tolerance during times of stress.
D) synthesizes gene transfer agents during stationary phase. | B) recognizes foreign DNA sequences that have previously entered the cell and directs the Cas proteins to destroy them. |
| UV radiation is a useful tool in producing mutants of microbial cultures. | TRUE |
| When UV radiation damage occurs, DNA repair occurs only in the absence of template instruction. | FALSE |
| Following uptake, transforming DNA becomes attached to a competence-specific protein that prevents it from nuclease attack until it reaches the chromosome. | TRUE |
| The evolutionary significance of phage conversion likely stems from an effective alteration of host cells. | TRUE |
| Bacterial mating (or conjugation) is a bidirectional process where nucleic acids (DNA or RNA) are transferred between two cells. | FALSE |
| Laboratory-based genetic systems have been difficult to develop for Archaea, because they do NOT naturally undergo conjugation or transduction. | FALSE |
| Almost all plasmids are double-stranded DNA. | TRUE |
| Most plasmids are circular rather than linear. | TRUE |
| When the F factor is integrated, all Hfr strains have the origin of replication functioning in the same direction. | FALSE |
| In a prokaryotic genome, either insertion elements OR transposons are present, but both are never present at the same time. | FALSE |
| The use of transposons to generate mutations is a convenient way to create bacterial mutations in the laboratory. | TRUE |
| Transposons can be found on many genetic elements, including plasmids, chromosomes, and viral genomes. | TRUE |
| In transformation experiments using a variety of Bacteria, it has been noted that essentially all of the cells in a population can become competent. | FALSE |
| In specialized transduction, virtually any genetic marker can be transferred from donor to recipient. | FALSE |
| In specialized transduction, as exemplified by lambda phage in E. coli, transduction occurs at high efficiency for only a restricted group of genes near the insertion site of lambda. | TRUE |
| Many Bacteria isolated from nature are natural lysogens. | TRUE |
| Lysogeny is essential for the virulence of many pathogenic bacterial strains. | TRUE |
| Proteins and nucleic acids absorb light maximally at 260 nm; hence, proteins protect cells from UV effects. | FALSE |
| Insertion sequences are found on both ends of transposons and encode for transposase. | TRUE |
| Toxigenicity in Corynebacterium diphtheriae is due to phage conversion. | TRUE |
| All Hfr strains possess an F factor integrated into the host chromosome. | TRUE |
| Penicillin selection is a positive selection for the isolation of mutants with growth factor requirements. | FALSE |
| Intercalating agents, like acridine orange and ethidium bromide, lead to mutagenesis by pushing DNA base pairs apart, which can lead to insertions or deletions. | TRUE |
| A typical mutation rate for a bacterium is in the range of 10-6 to 10-9 per kbp. | TRUE |
| Archaea have a unique form of conjugation involving cytoplasmic bridges for bidirectional transfer of DNA. | TRUE |
