Microbial Models: The Genetics of Viruses and Bacteria

The function of reverse transcriptase in retroviruses is to
1. hydrolyze the host cell's DNA
2. use viral RNA as a template for DNA synthesis.
3. convert host cell RNA into viral DNA
4. translate viral RNA into proteins
5. use viral RNA as a template for making complementary RNA strands.
The role of a metabolite that controls a repressible operon is to
1. bind to the promoter region and decrease the affinity of RNA polymerase for the promoter.
2. bind to the operator region and block the attachment of RNA polymerase to the promoter
3. increase the production of inactive repressor proteins
4. bind to the repressor protein and inactivate it
5. bind to the repressor protein and activate it
Viruses have some of the properties of living organisms. Which of the following is a characteristic of all organism, but NOT of viruses?
1. genetic information stored as nucleic acid
2. ability to control metabolism
3. ability to reproduce
4. structure includes proteins
5. plasma membrane
IN a hospital, a bacterium is isolated that is resistant to an antibiotic previously used against other kinds of bacteria. This is most likely the result of
1. transposition
2. reverse transcription
3. transduction
4. transformation
5. insertion
Which of the following is a TRUE statement about viruses?
1. Viruses are classified below the cellular level of biological organization
2. A virus particle contains both DNA and RNA
3. Individual virus particles are visible with light microscopes.
4. Assembly of viral capsids from proteins requires host cell assistance.
5. After assembly of the capsid, growth of virus particles continues until they are released.
A mutation that inactivates the regulator gene of a repressible operon in an E. coli cell would result in
1. continuous transcription of th estructural gene controlled by that regulator
2. complete inhibition of transcription of the structural gene controlled by that regulator
3. irreversible binding of the repressor to the operator
4. inactivation of RNA polymerase
5. Both B and C are correct
What is the function of the operator locus of an inducible operon?
1. producing repressor molecules
2. identifying the substrate lactose
3. producing messenger RNA
4. permitting transcription
5. binding steriod hormones
The tryptophan synthetase operon uses glucose to synthesize tryptophan. Repressible operons such as this one are
1. permantly turned on
2. turned on only when tryptophan is present in the growth medium
3. turned off only when glucose is present in the growth medium
4. turned on only when glucose is present in the growth medium
5. turned off whenever tryptophan is added to the growth medium
For a repressible operon to be transcribed, which of the following must be TRUE?
1. Corepressor must be present
2. RNA polymerase and the active repressor must be present
3. RNA polymerase must bind to the promotor and the repressor must be inactive.
4. RNA polymerase cannot be present and the repressor must be inactive.
5. RNA polymerase must not occupy the promotor and the repressor must be inactive.
The use of a phosphate isotope as a tracer element is the study of invasion and lysis of bacteria by bacteriophages has shown that
1. ATP from bacteriophages is identical to ATP found in eukaryotic cells
2. bacteriophage protein is infectious in bacteria
3. bacteriophage nucleic acid enters bacteria prior to lysis of the bacteria
4. phosphate isotopes accelerate the lytic effect of bacteriophage infection
5. phosphate isotopes in an inactive form enters the bacterial genome as a plasmid
Bactriophage DNAs that have become integrated into the host cell chromosome are called
1. intemperate bacteriophages
2. transposons
3. prophages
4. T-even bacteriophages
5. plasmids
Transcription of the structural gene in an inducible operon
1. occurs all the time
2. starts when the pathway's substrate is present
3. starts when the pathway's product is present
4. stops when the pathway's product is present
5. does not produce enzymes
____________ is a protein that is produced by a regulatory gene.
1. operon
2. operator
3. promoter
4. repressor
5. corepressor
____________ is a mutation in this gene could change the rate at which RNA polymerase binds to the DNA.
1. operon
2. operator
3. promoter
4. repressor
5. corepressor
____________ is a lack of this nonprotein molecule in the cellular environment would result in the inability of the cell to "turn off" genes.
1. operon
2. operator
3. promoter
4. repressor
5. corepressor
__________ is the binding of an active repressor molecule at this site prevents transcription.
1. operon
2. operator
3. promoter
4. repressor
5. corepressor
You would expect the lactose operon to be transcribed when
1. there is more glucose in the cell than lactose
2. there is more lactose in the cell than glucose
3. there is lactose but no glucose in the cell.
4. the cyclic AMP levels are high within the cell
5. Both C and D are correct
_____________ is a DNA segment that is moved from one location to another.
1. transduction
2. transposition
3. translation
4. transformation
5. conjugation
_______________ is DNA that is transfered from one bacterium to another by a virus.
1. transduction
2. transposition
3. translation
4. transformation
5. conjugation
____________ is DNA from one strain of bacteria that is assimilated by another strain.
1. transduction
2. transpostion
3. translation
4. transformation
5. conjugation
___________ is a plasmid that is exchanged between bacteria through a pilus.
1. transduction
2. transposition
3. translation
4. transformation
5. conjugation
____________ is DNA from pneumonia-causing bacteria that is mixed with harmless bacteria. The bacteria are injected into mice. The mice develop pneumonia and die.
1. transduction
2. transposition
3. translation
4. transformation
5. conjugation
A colony of antibiotic-resistant bacteria is mixed with a colony of anitbiotic-sensitive bacteria. After several days, all the bacteria are found to be resistant. This is results from _________________.
1. transduction
2. transposition
3. translation
4. transformation
5. conjugation
A group of F+ bacteria is mixed with a group of F- bacteria. After several days, all of the bacteria are F+. This results from ___________.
1. transduction
2. transposition
3. translation
4. transformation
5. conjugation
Bacterial strains "A" and "B" are growing together in a colony that has been infected with viruses. After a short period of time, a new strain of bacteria is detected that is very similar to strain "A" but has a few characteristics of strain "B". This results from
1. transduction
2. transposition
3. translation
4. transformation
5. conjugation
_____________ is when bacteria have proteins on the surface that recognize and take in DNA from closely related species.
1. transduction
2. transposotion
3. translation
4. transformation
5. conjugation
____________ results when a sequence of DNA that has inverted sequences on either end is found scattered throughout the chromosome of a bacterium
1. transduction
2. transposition
3. translation
4. transformation
5. conjugation
____________ results when antibiotic-resistant genes from different plasmids are found integrated into one large plasmid.
1. transduction
2. transposition
3. translation
4. tranformation
5. conjugation
_____________ results when DNA is present that does not provide any known benefit to the cell, yet is replicated each time the genome replicates
1. transduction
2. transposition
3. translation
4. transformation
5. conjugation
Which of the following represents a difference between viruses and viroids?
1. Viruses infect many types of cells, while viroids infect only prokaryotic cells.
2. Viruses have capsids composed of protein, while viroids have no capsids.
3. Viruses contain introns; viroids have only exons.
4. Viruses have genomes composed of DNA; while viroids have genomes composed of RNA.
5. Viruses cannot pass through plasmodesmata; viroids can.
A researcher lyses a cell that contains nucleic acid molecules and capsid units of TMV. He leaves this sap in a covered test tube overnight. The next day he sprays this fluid on tobacco plants. Which of the following would you expect to occur?
1. The plants would develop some but not all of the symptoms of the TMV infection.
2. The plants would develop symptoms typically produced by viroids.
3. The plants would develop the typical symptoms of TMV infection.
4. The plants would not show any disease symptoms.
5. The plants would become infected, but the sap from these plants would be unable to infect other plants.
Which of the following statements best describes oncogenes?
1. They are found only in tumor cells.
2. They are found only in tumor-causing viruses.
3. They code for growth factors or proteins associated with grwoth factors.
4. Activation of a single oncogene can transform a healthy cell.
5. Both A and B accurately describe oncogenes.
Most molecular biologists believe that viruses originated from fragments of cellular nucleic acid. Which of the following observations supports this theory?
1. Viruses contain either DNA or RNA.
2. Viruses are enclosed in protein capsids rather than plasma membranes.
3. Viruses can reproduce only inside host cells.
4. Viruses can infect both prokaryotic and eukaryotic cells.
5. Viral genomes are usually more similar to the genome of the host cell than to the genome of other cells.
What is the most common source of genetic diversity in a bacterial colony?
1. transposons
2. plasmids
3. recombination
4. crossing over
5. mutation
In which of the following cases would a mutation have the most significant impact on the genetic diversity of a species?
1. The species reproduces only asexually.
2. The species reproduces only sexually.
3. The species usually reproduces asexually, but can reproduce sexually when conditions become unfavorable.
4. The species has a relatively long reproductive cycle.
5. The species' reproductive cycle is unpredictable.
Reproduction in bacteria requires
1. the production of a mitotic spindle
2. a plasmid
3. cyclic AMP
4. replication of DNA
5. Both B and D.
Which of the following statements regarding transposons is FALSE?
1. Transposons have specific target sites within the genome.
2. Transposons are found in both prokaryotes and eukaryotes.
3. Transposons can move from a plasmid to the chromosome of the bacterium
4. Transposons may replicate at the original site and insert the copy at another site.
5. Transposons may carry only the genes necessary for insertion.
An Hfr bacterium is one that has
1. at least one plasmid present in the cytosol
2. a special recognition site that will take up closely related DNA from its environment.
3. several insertion sequences scattered throughout its chromosome.
4. several copies of a single transposon repeated randomly throughout its chromosome.
5. a plasmid that has become integrated into its chromosome.
Two strains of Hfr cells were allowed to conjugate. The conjugation was interrupted at 5-minute intervals and the following fragments were obtained: ZDKP, LYMG, AZDK, KPVQ, QLYM. What is the correct sequence for these genes in the chromosome?
1. DKPLYMQVPGA
2. AZDKPVQLYMG
3. YLQVMGAZDKP
4. GMLYQZVPKDA
5. GVMQYLAZDPK
A virus injects its DNA into a cell. Some genes are transcribed rapidly. Those genes are probably involved in
1. producing DNA polymerase
2. producing virual capsule proteins
3. producing repressor proteins to control the bacterial cell.
4. producing proteins that lyse the bacterial cell.
5. producing various enzymes to alter cellular metabolism
For many bacteriophages, infections are self-limiting. Each phage that infects a cell produces hundreds of new phages, and eventually cells are infected by several phages at different times. This results in a competition for regulatory control over the cell, with the eventual result of the death of the cell without a production of new viruses. This phenomenon is called "superinfection." Superinfection can be prevented by which of the following changes in the bacteriophage?
1. restricting the host range of the phage.
2. slowing down the rate of the lytic infection
3. making larger numbers of new phages
4. the virus becoming a prophage in the cell
5. evolving a more complex protein coat
The "central dogma" of molecular genetics is a statement describing the flow of information in a cell. DNA makes RNA which makes proteins. This path is not reversible. The exception to part of this statement seems to be
1. retroviruses
2. temperate phages
3. herpesviruses
4. tumor viruses
5. all viruses
Which of the following does NOT consist of a sequences of bases?
1. repressor
2. structural gene
3. promoter
4. regulator gene
5. operator
Virulent phages undergo a(n) _______ life cycle, whereas temperate phages are capable of undergoing a(n) ________ cycle.
1. infective; retroviral
2. lysogenic; lytic
3. lytic; lysogenic
4. retroviral;infective
5. infective; benign
RNA viruses occur in three different types. One of those has only a single strand of RNA. That single strand serves which purpose?
1. It becomes an mRNA
2. It codes for an mRNA
3. It is used as a template for the synthesis of more RNA.
4. It is used as a template for the synthesis of DNA
5. It becomes a prophage.
Viruses that have only a single strand of RNA are known as
1. retroviruses
2. proviruses
3. viroids
4. bacteriophages
5. lytic phages
Of the following, which is LEAST related to the others?
1. R plasmids
2. episomes
3. prions
4. nucleoids
5. F factors
Of the following, which is LEAST related to the others?
1. viral envelope
2. viroids
3. provirus
4. prophage
Of the following, which is LEAST related to the others?
1. transduction
2. conjugation
3. induction
4. transposition
5. transformation
Of the following, which is LEAST related to the others?
1. prion
2. regulatory gene
3. promoter
4. operator
5. repressor
Of the following, which is LEAST related to the others?
1. corepressor
2. repressor
3. inducer
4. transposon
5. cAMP receptor protein
The host range of a virus is determined by
1. the viral coat
2. whether the virus uses DNA or RNA
3. proteins on the surface of the cell
4. enzymes produced by the virus before it infects the cell
5. both A and C
Which of the following affects the ability of the immune system to develop resistance to a viral infection?
1. vaccine
2. prophages
3. viral envelopes
4. transposons
5. viroids
RNA viruses appear to have higher rates of mutation because
1. RNA nucleotides are more unstable than DNA nucleotides
2. the enzyme reverse transcriptase does not proofread the was DNA polymerase does
3. RNA viruses replicate faster
4. RNA viruses can incorporate a variety of nonstandard bases.
5. RNA viruses respond more to mutagens
Which of the following does NOT contribute to the emergence of viral disease?
1. production of new strains of virus through mutation
2. spread of existing virus from one host to another
3. transformation from lytic to lysogenic activity
4. dissemination from a small, isolated host population
Prions are infectious particles that are unique in that they are believed to lack
1. DNA
2. RNA
3. proteins
4. any nucleic acid
5. a membrane