Microbiology: Chapter 16

DNA molecules that enter a bacterium by one of several mechanisms is called a(n) A. merozygote. B. exogenote. C. endogenote. D. none of the choices

B. exogenote.

Which of the following is considered a reverse mutation that will restore the wild type phenotype? A. True reversion back to the wild type base sequence. B. Mutation to a different base sequence, but one that restores the amino acid sequence in the protein to the wild type sequence. C. A mutation that restores the function of a protein even though it does not restore the base sequence or the amino acid sequence to the wild type. D. All of the choices.

D. All of the choices.

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

D. all of the choices

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

False

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

Host restriction

__________ mutations affect only a single base pair in a gene.

Point

T/F: Approximately half of known animal carcinogens can be detected by the Ames test.

True

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

True

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

True

Mutations resulting from exposure to physical or chemical agents are called __________ mutations.

induced

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

plasmid

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.

under (or less)

The __________ __________ is the most prevalent form of a gene in a population.

wild type

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)

A. F+

After an F+ F- mating, the donor is __________ and the recipient is __________. A. F+; F- B. F-; F+ C. F-; F- D. F+; F+

A. F+; F-

Who is credited with demonstrating unidirectional and nonreciprocal transfer of DNA between two mating E. coli cells? A. Hayes B. Lederberg C. Tatum D. none of the choices

A. Hayes

The Ames test A. can be used to measure the mutagenicity of chemicals. B. is used to measure the repair of thymine dimers. C. is used to measure levels of oxygen free radicals. D. none of the choices

A. can be used to measure the mutagenicity of chemicals.

A mutation from the most prevalent form of a gene to a mutant form is called a __________ mutation. A. forward B. reverse C. wild card D. escalating

A. forward

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

A. homologous

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.

A. horizontal gene transfer.

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

A. insertion sequences

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

A. merozygote

A mutation that changes the amino acid sequence of the resulting protein by substitution is called a __________ mutation. A. missense B. nonsense C. silent D. none of the choices

A. missense

_______ are strains that are unable to grow on a minimal medium that supports growth of the wild type strain but are able to grow on the minimal medium if one or more nutritional supplements are added. A. Autotrophs B. Auxotrophs C. Prototrophs D. Minitrophs

B. Auxotrophs

When an F plasmid integrates into the host chromosome, the strain is referred to as A. F+. B. Hfr. C. F'. D. F-.

B. Hfr.

Which of the following best represents the order of gene transfer in an Hfr F- mating? 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.

B. Part of the plasmid followed by the chromosome followed by the rest of the plasmid.

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.

B. may be involved in the spread of antibiotic resistance in bacteria.

Which of the following types of mutation may play an important role in driving evolution because they are often nonlethal and, therefore, remain in the gene pool? A. nonsense B. missense C. frameshift D. deletion

B. missense

A __________ mutation is one that causes premature termination of the synthesis of the protein product. A. missense B. nonsense C. silent D. none of the choices

B. nonsense

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

B. photoreactivation

Lethal mutations can be maintained in diploid organisms if they are A. dominant. B. recessive. C. deletions. D. none of the choices

B. recessive.

Plasmids that have genes that decrease bacterial susceptibility to antibiotics are called __________ factors. A. col B. resistance C. virulence D. metabolic

B. resistance

When a recipient cell acquires a piece of naked DNA from the environment, it is called A. conjugation. B. transformation. C. transduction. D. transfection.

B. transformation.

As the result of exposure to a mutagen, cytosine is substituted for thymine in one strand of DNA. Upon subsequent DNA replication, one of the daughter cells will have a GC pair in this position instead of an AT pair. This is called a(n) __________ mutation. A. transversion B. transition C. frameshift D. insertion

B. transition

Complete transfer in an Hfr F- mating takes approximately __________ minutes. A. 20 B. 50 C. 100 D. 200

C. 100

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.

C. DNA polymerase I.

Which of the following can lead to transition mutations? A. Incorporation of a base analog that exhibits different base-pairing properties from the base it replaces. B. Chemical modification of an existing base in the DNA so that in the next round of replication it will pair differently from the unmodified base. C. Incorporation of a base analog that exhibits different base-pairing properties from the base it replaces and chemical modification of an existing base in the DNA so that in the next round of replication it will pair differently from the unmodified base. D. A small insertion or deletion.

C. Incorporation of a base analog that exhibits different base-pairing properties from the base it replaces and chemical modification of an existing base in the DNA so that in the next round of replication it will pair differently from the unmodified base.

Which of the following is the most error-prone of the repair mechanisms? A. postreplication repair B. recombination repair C. SOS repair D. photoreactivation

C. SOS repair

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

C. Some chromosomal genes not on the plasmid are transferred.

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 these are true of specialized transduction.

C. The phage genome retains the full complement of phage genes.

Alternate forms of genes resulting from mutations are called A. isoforms. B. alterons. C. alleles. D. lethal.

C. alleles.

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

C. an integrated F plasmid is incorrectly excised, bringing host genes with it.

Lethal mutations can be recovered in haploid organisms if they are A. dominant. B. active. C. conditional. D. none of the choices

C. conditional.

The genome of a recipient cell is called a(n) __________. A. merozygote B. exogenote C. endogenote D. none of the choices

C. endogenote

A mutagen that inserts between the stacked bases of a DNA double helix, distorting the DNA to induce single-pair insertions or deletions is called a(n) __________ agent. A. insertional B. interspersing C. intercalating D. distortional

C. intercalating

Mutations that result in the death of an organism when expressed are called __________ mutations. A. dominant B. recessive C. lethal D. conditional

C. lethal

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

C. only those temperate bacteriophages that integrate into the host chromosome.

Microbial strains that can grow on minimal medium are called __________. A. autotrophs B. auxotrophs C. prototrophs D. minitrophs

C. prototrophs

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.

C. recombination.

A __________ mutation does not alter the amino acid sequence of the resulting protein. A. missense B. nonsense C. silent D. none of the choices

C. silent

When bacterial genes are transferred to another bacterium by a virus, it is called A. conjugation. B. transformation. C. transduction. D. transfection.

C. transduction.

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 true.

D. All of the choices are true.

Which of the following effects may be mediated by transposable elements? A. Insertion into a gene, causing a mutation. B. Activation of nearby genes. C. Formation of genetic deletions. D. All of the choices.

D. All of the choices.

Which of the following is a possible fate for an exogenote? A. Integration into the host chromosome. B. Independent replication and functioning. C. Degradation to nucleotides. D. All of the choices.

D. All of the choices.

Which of the following occurs with generalized transduction? A. Degradation of the host chromosome into randomly sized fragments. B. Packaging of any DNA fragment of the appropriate size. C. Transfer of any bacterial gene to the subsequent host. D. All of these occur with generalized transduction.

D. All of these occur with generalized transduction.

Which of the following is true of the integration of a viral genome into the host chromosome? A. It is a form of site-specific recombination. B. The enzymes are specific for the virus and its host. C. Integration begins the process of host chromosome degradation. D. It is a form of site-specific recombination and the enzymes are specific for the virus and its host.

D. It is a form of site-specific recombination and the enzymes are specific for the virus and its host.

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

D. all of the choices

Which one of the following contributes to the utility of the strains of Salmonella typhimurium used in the Ames reversion assay? A. They are highly permeable to test substances. B. They are defective in DNA repair and, therefore, cannot readily repair damage done by the test substances. C. It is very straightforward to assay the conversion of their histidine auxotrophy mutations to histidine prototrophy. D. all of the choices

D. all of the choices

Transfer of genetic information via direct cell-cell contact is called A. transformation. B. transduction. C. transfection. D. conjugation.

D. conjugation.

Spontaneous mutations are caused by A. errors in DNA replication. B. insertion of transposons. C. radiation. D. errors in DNA replication and insertion of transposons E. all of the choices

D. errors in DNA replication and insertion of transposons

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

D. heteroduplex

Transposons that transpose by inserting a copy at a new location while a copy remains at the original location are said to transpose by _______________ transposition. A. simple B. composite C. incomplete D. replicative

D. replicative

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

False

T/F: 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+.

False

T/F: 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.

False

__________ are physical or chemical agents that cause mutation.

Mutagens

__________ mutations occur in the promoter or operator region of a gene or set of genes and affects the expression of the downstream genes without affecting the amino acid sequences of the gene products.

Regulatory

T/F: Photoreactivation repairs thymine dimers by splitting them back into separate thymines.

True

T/F: 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.

True

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.

competent

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

conjugative

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

episome

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

prophage