microbio exam 3
Lethal mutations can be maintained in diploid organisms if they are ________. A) dominant B) recessive C) deletions D) None of the choices are correct.
B
The genome of a recipient cell is called a(n) ________. A) merozygote B) exogenote C) endogenote D) None of the choices are correct.
C
Photoreactivation repairs thymine dimers by splitting them back into separate thymines.
T
The basic differences between RNA and DNA reside in their sugar and pyrimidine bases; RNA has ribose and uracil whereas DNA has deoxyribose and thymine.
T
If a set of genes is repressed in the presence of the controlling substance, it is referred to as ________ control.
negative
Messenger RNA molecules have a nontranslated sequence called the ________, which is located downstream of the termination codon.
trailer
How many phosphodiester bonds are needed to join 50 deoxyribonucleotides in a DNA strand? A) 49 B) 50 C) 51 D) 100 E) 102
A
In terms of transcription regulation, the role of a helix-turn-helix is most similar to that of a(n) . A) zinc finger B) sigma factor C) poly-A tail D) guanine cap
A
10) Select the secretion systems that are found in both Gram-positive and in Gram-negative bacteria. A) Type 1 B) Type II C) Type III D) Type IV
A,D
The genetic code is translated in groups of ________ bases. A) two B) three C) four D) five
B
Which is a false statement regarding riboswitches? A) Riboswitches are regions in the 5' untranslated leader of an mRNA. B) The effector molecules that bind to riboswitches are proteins. C) When the effector binds the riboswitch, it may serve to terminate transcription of its target mRNA. D) When the effector binds the riboswitch, it may serve to continue transcription of its target mRNA.
B
A ________ mutation does not alter the amino acid sequence of the resulting protein. A) missense B) nonsense C) silent D) None of the choices are correct.
C
When a DNA molecule is replicated, the daughter molecules contain one strand of parental DNA and one strand of newly synthesized DNA; this is called ________ replication. A) hemiconservative B) conservative C) semiconservative D) dispersive
C
During regulation of biofilm formation in Pseudomonas, cells leave the biofilm when levels of cyclic dimeric GMP are high.
F
Mutations resulting from exposure to physical or chemical agents are called ________ mutations.
INDUCED
Approximately half of known animal carcinogens can be detected by the Ames test.
T
A molecule of RNA has 99 phosphodiester bonds connecting ________ ribonucleotides.
100
Order the following regions of a gene from the most upstream region (1) to the most downstream region (5). 1. -35 consensus sequence 2. Pribnow box 3. coding sequence 4. rut site 5. terminator
3, 4, 1, 2, 5
If the product of a functional gene is not a protein, what other product(s) might be encoded by the gene? A) tRNA and rRNA B) tRNA and mRNA C) mRNA and rRNA D) mRNA, tRNA, and RNA
A
In ________, ribosomes can attach to the mRNA and begin translation even though transcription has not been completed. A) bacteria B) eukaryotes C) fungi D) protozoa and some plants
A
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
One benefit of transporting molecules via outer membrane vesicles and extracellular vesicles versus a typical secretion system is that ________. A) the vesicle contents are protected by the lipid bilayer that surrounds them, extending their viability outside of the cell B) transport from one cell to another occurs at a much more rapid rate C) it requires much less energy to transport the molecules in vesicles D) vesicles form regardless of the environmental conditions that surround the bacterial cells
A
Predict the outcome of protein synthesis if a gene undergoes a mutation in its anticodon region where a charged tRNA recognizes a nonsense mutation. A) Transcription and translation both would continue. B) Transcription would continue but translation would not continue. C) Transcription and translation both would not continue. D) Transcription would not continue but translation would continue.
A
What would be the hypothetical outcome if the action of RecA was 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.
A
What would be the most likely outcome if the genetic code was not degenerate? A) The effect of some mutations would increase. B) The effect of some mutations would decrease. C) The mutation rate would remain the same. D) The number of stop codons would increase.
A
Which of the following is a correct comparison between RNA polymerase holoenzyme that functions in transcription and the primase enzyme that functions in DNA replication? A) Both enzymes synthesize RNA. B) Both enzymes are bound by sigma factor. C) Both enzymes synthesize DNA. D) Both enzymes are composed of RNA.
A
Which of the following is a region of DNA at the end of a linear chromosome? A) Telomere B) Primer C) Intron D) Exon
A
Which of the following is the initiator codon? A) AUG B) UAA C) UAG D) UGA
A
Which statement defends the concept that the term "gene" is better defined as a nucleotide sequence that encodes for one or more functional products rather than encoding for one or more functional proteins? A) Products of genes include ribonucleotides as well as proteins. B) Intron sequences in DNA do not encode proteins. C) The genetic code is redundant, therefore the same codon may be encoded by different DNA triplets. D) Genes in bacteria are organized as operons that can lead to several protein products.
A
Which of the following are exceptions to the universal genetic code that is used by most organisms? A) Selenocysteine B) Stop C) Pyrrolysine D) Lysine E) Phenylalanine
A,C
The two strands of a DNA molecule are ________; that is, they are oriented in opposite directions.
ANTIPARALLEL
) During sporulation in Bacillus subtilis, the response regulator that positively controls many genes needed for sporulation and negatively controls genes not needed during sporulation is ________. A) SpoOB B) SpoOA C) SpoOF D) SpoOC
B
A bacterial ________ is the nontranscribed region of the DNA to which RNA polymerase binds in order to initiate transcription. A) operon B) operator C) promoter D) initiator
C
Alternate forms of genes resulting from mutations are called ________. A) isoforms B) alterons C) alleles D) lethal
C
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
The unexpressed regions of split genes are called ________. A) exons B) endons C) introns D) codons
C
When bacterial genes are transferred to another bacterium by a virus, it is called ________. A) conjugation B) transformation C) transduction D) transfection
C
When bound to the DNA, the repressor protein usually prevents attachment of the RNA polymerase to the ________. A) operon B) operator C) promoter D) regulator
C
Which of the following is not a regulatory mechanism used to control the lactose operon in Escherichia coli? A) Induction B) Catabolite repression C) Attenuation D) All of the choices are correct.
C
Acylhomoserine lactones used in quorum sensing regulate their own synthesis by a(n) ________ system. A) riboswitch B) antisense C) catabolite repression D) autoinduction
D
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.
D
Hershey and Chase demonstrated that when the bacteriophage T2 infected its host cell, the ________ is injected into the host but the ________ remained outside.
DNA; protein
A plasmid that can either exist independently of the chromosome or be integrated into it is called a(n) ________.
EPISOME
A cell that is Hfr and a cell that is F+ can be the same cell.
F
Acridine orange is a purine base analogue.
F
Riboswitches regulate transcription, rather than translation, in cells.
F
________ is used to measure the amount of a chemoattractant encountered over time.
METHYLATION
The transcribed and translated region of a gene is the ________ region. A) leader B) promoter C) coding D) trailer
c
In order for high level expression of the E. coli lac operon to occur, a complex of catabolite activator protein and ________ must be bound to the DNA near the promoter.
cAMP
Proteins that recognize unfolded polypeptides and help them fold into their proper conformations are called ________.
chaperones
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
On mRNA molecules, a nontranslated sequence called the ________ usually precedes the initiation codon.
leader
Messenger RNA molecules that direct the synthesis of more than one polypeptide are said to be ________.
polycistronic
If a set of genes is induced in the presence of the controlling substance, it is referred to as ________ control.
positive
A(n) ________ is a latent form of a virus genome that remains within the host without destroying it.
prophage
When there is no arabinose available in the environment, the AraC protein acts as a(n) ________ for the E. coli ara operon.
repressor
The ________ ________ is the most prevalent form of a gene in a population.
wild type
A ________ is a piece of extrachromosomal DNA that has its own replication origin.
PLASMID
) Serratia marcescens bacteria has a gene that regulates red pigment production by cells. A student inoculates two nutrient agar plates of Serratia and incubates one at 25oC and the other at 37oC. Following incubation, the student observes that colonies on the 25oC plate are red while those on the 37oC plate are nonpigmented. Which of the following statements is a logical conclusion based on these results? A) Serratia genes for pigment production are induced at certain temperatures. B) This is an example of constitutive gene expression. C) Low temperatures cause repression of certain housekeeping genes. D) Serratia cells undergo a genotypic change that is proportional to changes in temperature.
A
A complex consisting of a single mRNA molecule with several ribosomes is called a ________. A) polysome B) multisome C) maxisome D) proteosome
A
A microbial geneticist observes that a significant number of pyrimidine dimers are present in bacterial DNA following exposure to a particular mutagen. To which mutagen were the bacterial cells likely exposed? A) UV light B) Acridine orange C) 5-bromouracil D) X-rays
A
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 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.
A
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 are 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.
A
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
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 are correct.
A
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.
A
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.
A
A reciprocal exchange in which two DNA molecules 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.
A
A scientist wishes to develop an antimicrobial agent that specifically targets replication elongation in Escherichia coli without interfering with proteins that catalyze other replication processes. Which of the following experimental designs is most appropriate for the scientist to explore? A) Develop a molecule that interferes with the DNA-binding ability of DNA polymerase III core enzyme B) Modify an existing antibiotic to act as a competitive inhibitor of DNA polymerase I C) Design a drug that modifies the structural configuration of DNA at the oriC locus D) Create a novel protein that acts as a competitive inhibitor of the DNA ligase binding site
A
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
A
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−.
A
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
A
An sRNA is isolated from a bacterial cell. What would you do to determine whether it is a cis-encoded or a trans-encoded sequence? A) Identify whether or not the sRNA sequence is complementary to the coding strand of mRNA gene target. B) Analyze the molecular position of hydrogen atoms in the sRNA nucleotides. C) Determine whether the sRNA binds to mRNA or to tRNA. D) Find out if the sRNA acts as a transcriptional or as a translational inhibitor.
A
Bacterial DNA replication occurs at a rate of ________. A) 750-1,000 base pairs per second B) 750-1,000 base pairs per minute C) 50-100 base pairs per second D) 50-100 base pairs per minute
A
Bacterial responses to phage infection can be compared to the human immune system. Which of the phrases is true? A) Restriction-modification can be compared to innate immunity and CRISPR/Cas to adaptive immunity. B) Restriction-modification can be compared to adaptive immunity and CRISPR/Cas to innate immunity. C) Restriction-modification can be compared to the complement system and CRISPR/Cas to inflammation. D) Restriction-modification can be compared to B cell responses and CRISPR/Cas to T cell responses.
A
Bacterial ribosomes ________. A) comprise two rRNA subunits, multiple proteins, and three tRNA binding sites B) comprise two tRNA binding sites, three rRNA subunits, and multiple proteins C) comprise two proteins, three tRNA binding sites, and multiple rRNA subunits D) comprise multiple tRNA binding sites, three proteins, and two rRNA subunits
A
Bioluminescence in Vibrio fischeri is dependent on ________. A) autoregulation of the luxI gene B) destabilization of luxM mRNA C) posttranslational regulation of Spo0A protein D) phosphorylation of CheY protein
A
Choose the correct order of proteins that function in the initiation, elongation, and termination stages of DNA replication. A) DnaA, DNA polymerase III, DNA polymerase I, DNA ligase B) DnaA, DNA polymerase I, DNA polymerase III, DNA ligase C) DNA polymerase III, DNA polymerase I, DNA ligase, DnaA D) DNA polymerase I, DnaA, DNA polymerase III, DNA ligase
A
Choose the description below that best matches the current model of RNA polymerase holoenzyme. A) A core enzyme composed of five polypeptides bound by a transcription factor. B) A core enzyme composed of five polypeptides bound by ribosomes. C) A core enzyme composed of five sigma factors bound by a polypeptide chain. D) An open complex or "bubble" formed by DNA, mRNA, and RNA polymerase.
A
DNA polymerases require which of the following elements to replicate DNA? A) A template, a primer, a source of energy B) A source of energy, an RNA strand, a ribosome C) A ribosome, a template, an RNA polymerase D) A source of energy, a template, an RNA polymerase
A
During ________ proteins are moved from the cytoplasm to the membrane or periplasmic space, while during ________ proteins are moved from the cytoplasm to the external environment. A) translocation; secretion B) secretion; translocation C) transcription; translation D) translocation; translation E) secretion; translation
A
During sporulation in Bacillus subtilis, inactive precursor forms of new sigma factors are activated at the appropriate time by which mechanism? A) Proteolysis B) Phosphorylation C) RNA-binding D) Chaperone refolding
A
During transcription elongation, how many pyrophosphate molecules are produced from the incorporation of 20 ribonucleoside monophosphates? A) 20 B) 40 C) 60 D) 5
A
Griffith's experiment demonstrated transformation because a mouse injected with live R and heat-killed S strains of Streptococcus pneumoniae resulted in death of the mouse and the isolation of live R as well as live S cells. Hypothesize as to the type of cells that Griffith would have observed if transformation had NOT occurred. A) Griffith would have isolated only live R cells from the mouse host. B) Griffith would have isolated both live R and heat-killed S cells from the mouse host. C) Griffith would have isolated only live S cells from the mouse host. D) Griffith would have isolated no cells from the mouse host.
A
Homologous recombination differs from site-specific recombination in that ________. A) homologous recombination involves long stretches of similar-sequence nucleotides on two DNA molecules that break and reanneal in a crossover mechanism, whereas site-specific recombination occurs at target sites, catalazed by recombinases B) homologous recombination takes place at specific target sites catalazed by recombinases, whereas site-specific recombination involves long stretches of same-sequence nucleotides on two DNA molecules that break and reanneal in a crossover mechanism C) homologous recombination takes place in eukaryotic cells during meiosis, whereas site-specific recombination takes place in bacteria and archaea during horizontal gene transfer D) homologous recombination utilizes enzymes collectively called recombinases, whereas site-specific recombination involves RecA to bring about the crossover between DNA molecules
A
How could the Hershey and Chase experimental procedure be redesigned to support a hypothesis that RNA carries genetic information? A) Replace T2 bacteriophage with an RNA virus B) Replace Escherichia with an RNA virus C) Use 35S to label an RNA virus and 32P to label a DNA virus D) Extract RNA from Escherichia and mix it with the T2 bacteriophage E) Use 35S and 32P to label the same components of an RNA virus and T2 bacteriophage, then add both viruses to Escherichia cells
A
How do translational riboswitches and transcriptional riboswitches differ? A) Translational riboswitches are mainly observed in Gram-negative bacteria while transcriptional riboswitches are associated with Gram-positive bacteria. B) Translational riboswitches are located in the mRNA trailer while transcriptional riboswitches are in mRNA leader sequence. C) Translational riboswitch effectors bind to ribosomes while transcriptional riboswitch effectors bind to mRNA. D) All of these are differences between translational and transcriptional riboswitches.
A
How many RNA codons encode 60 amino acids? A) 60 B) 180 C) 20 D) 30
A
How were experiments done by Griffith similar to those done by Avery, MacLeod, and McCarty? A) Both used pneumococcal bacteria B) Both used purified DNA C) Both used a mouse host D) Both were done in the 1940s E) Both used enzymes that destroyed DNA
A
IF 20% of nucleotides in the DNA of a particular organism contain thymine, estimate the percentage of cytosine that is present in the DNA. A) 30% B) 20% C) 15% D) 80% E) 40%
A
If Escherichia coli is cultured in broth containing both glucose and lactose, it ________. A) uses glucose preferentially until the supply is exhausted, then uses lactose B) uses lactose preferentially until the supply is exhausted, then uses glucose C) uses glucose and lactose simultaneously D) uses only the glucose (it cannot use lactose as a source of carbon)
A
If autophosphorylation of CheA protein does not occur, then Escherichia coli cells must be ________. A) in a gradient of a chemoattractant B) in a gradient of a chemorepellant C) tumbling D) rotating flagella clockwise
A
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.
A
If flagellar rotation of Escherichia coli cells is ________, then CheA is ________. A) counterclockwise; unphosphorylated B) counterclockwise; autophosphorylated C) clockwise; autophosphorylated D) clockwise; unphosphorylated
A
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.
A
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.
A
If you were to design a novel hydrophobic protein, which type of monomers would be most essential to incorporate in the molecule in order to achieve the desired result? A) Amino acids with nonpolar side chains B) Amino acids with charged side chains C) Purine-containing deoxyribonucleotides D) Hydrophobic nucleic acids E) Polar amino acids
A
If you wished to design an antimicrobial agent that prevented the formation of the 70S initiation complex in bacterial translation, which molecule should specifically be targeted? A) IF-3 B) mRNA C) Peptidyl transferase D) EF-1
A
In attenuation regulation of the trp operon, which stem loop forms when tryptophan is readily available to the cell? A) 3:4 B) 1:3 C) 2:3 D) 2:4
A
In bacteria, splicing of proteins occurs ________. A) cotranslationally, and minimally involves splicing the N-formyl group from the initiator amino acid as it exits the ribosome B) posttranslationally, and minimally involves splicing the N-formyl group from the initiator amino acid as it exits the ribosome C) posttranslationally, and always involves splicing the first two amino acids from the N-terminus as it exits the ribosome D) cotranslationally, and always involves splicing the first two amino acids from the N-terminus as it exits the ribosome
A
In catabolite repression systems of some Gram-positive bacteria, such as Bacillus subtilis, transcription of catabolic operons is regulated by CcpaA (catabolite control protein A) rather than cAMP. Propose a hypothesis to explain the preferential use of glucose in the presence of a second sugar such as sucrose by Bacillus subtilis. A) CcpaA acts as a repressor of sucrose operon genes in Bacillus subtilis when both sugars are present. B) CcpaA acts as an inducer of sucrose operon genes in Bacillus subtilis when both sugars are present. C) CcpaA acts as a repressor of sucrose operon genes in Bacillus subtilis when lactose, but not glucose, is present. D) CcpaA acts as an inducer of sucrose operon genes in Bacillus subtilis when glucose, but not lactose, is present.
A
In terms of global gene regulation, which of the following molecules is most similar to c-di-GMP and cAMP? A) ppGpp B) rRNA C) ATP D) EnvZ
A
In terms of relatedness to a specific cellular process, which protein does not belong with the others? A) RNA polymerase holoenzyme B) DNA polymerase holoenzyme C) Ribonuclease D) DNA ligase
A
In the CRISPR/Cas system ________. A) bacteria integrate portions of the viral genome into their own so they have a molecular snapshot of their attacker to prevent future encounters B) restriction endonucleases digest viral genomes once they enter the cell if the viral DNA is not methylated C) methylase enzymes add methyl groups to the viral nucleic acids, preventing transcription D) methylated DNA sequences are hydrolyzed, effectively destroying the viral DNA
A
In the Hershey and Chase experiment, how did labeling DNA and protein with different radioactive isotopes demonstrate that DNA, rather than protein, carried the genetic information in the T2 virus? A) Researchers could track which part of the virus entered a bacterial cell. B) Researchers could use radio labeling to inactivate DNA and protein in the bacteria. C) Researchers could distinguish bacterial DNA from viral protein. D) Researchers could better elucidate DNA or protein structure. E) Researchers could monitor how DNA interacted with protein in the virus.
A
In which situation might methylation of membrane proteins in Escherichia coli initiate a phosphorelay system that evokes clockwise rotation of flagella? A) Presence of a chemorepellent in the extracellular environment B) Change in environmental osmotic pressure C) Utilization of lactose due during diauxic growth D) Cellular population reaches a quorum
A
Mobilizable genomic islands (MGIs) differ from integrative conjugative elements (ICEs) in that ________. A) MGIs include an att site, allowing large portions of the bacterial chromosome to be transferred, whereas ICEs are transposons in nature B) MGIs are insertion sequences, whereas ICEs are transposons C) MGIs are transferred by conjugation, whereas ICEs are transferred by transduction D) MGIs transfer pathogenicity islands, whereas ICEs transfer antibiotic-resistance genes
A
Modify the following statement to make it correct: Ribozymes are ribonucleosomes used by bacteria and eukaryotic cells to modify DNA. A) Ribozymes are ribonucleases used by bacteria and eukaryotic cells to modify RNA. B) Ribozymes are ribonucleosomes used by bacteria and eukaryotic cells to modify RNA. C) Ribozymes are ribonucleases used by bacteria and eukaryotic cells to modify DNA. D) Ribozymes are ribonucleosomes used only by eukaryotic cells only to modify RNA.
A
Ribosomes consist of ________ separate subunits that come together as part of the initiation process and dissociate immediately after termination. A) two B) three C) four D) five
A
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 are correct.
A
The Sec system is used by ________. A) both Gram-positive and Gram-negative bacteria B) neither Gram-positive nor Gram-negative bacteria C) Gram-positive bacteria only D) Gram-negative bacteria only
A
The activity of adenyl cyclase is influenced by ________. A) the phosphotransferase system B) the presence of lactose in the environment C) homoserine lactones D) None of the choices are correct.
A
The coding sequence in the DNA of ________ is normally continuous; that is, it is not interrupted by noncoding sequences. A) bacteria B) plants C) mammals D) most insects
A
The standard or housekeeping sigma factor used most often by E. coli RNA polymerase under normal growth conditions is called sigma ________. A) 70 B) 32 C) S D) E
A
The terminator versus anti-terminator function of the T box-based riboswitch used by Gram-positive bacteria to regulate amino acid-related genes is determined by ________. A) the binding of the appropriate uncharged tRNA B) the rate of leader peptide synthesis C) the binding of the T box binding protein D) the utilization of the appropriate sigma factor by RNA polymerase
A
The transcribed, but not translated, sequence that is immediately upstream of the region that encodes the functional product is called the ________ region. A) leader B) promoter C) coding D) trailer
A
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
Two amino acids that are found in some proteins due to exceptions in the universal genetic code are ________. A) pyrrolysine and selenocysteine B) lysine and selenocysteine C) pyrrolysine and cysteine D) lysine and cysteine
A
What is the function of cyclic dimeric GMP in bacterial global regulation systems? A) It acts as a secondary nucleotide messenger B) It is a sensor kinase C) It converts GTP to cGTP D) It is an autoinducer
A
What is the minimum number of aminoacyl-tRNA synthetase enzymes needed to attach amino acids to all the various tRNA molecules? A) 20 B) 61 C) 64 D) As many as there are different tRNAs
A
What might be a reason for the accumulation of improperly folded protein complexes in the bacterial cell cytoplasm following translation? A) A problem exists with the functioning of molecular chaperones B) The cell is synthesizing proteins too rapidly C) Polysomes are forming on the mRNA D) The proteins are being transcribed but not translated
A
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.
A
When a protein is synthesized, cis- or trans-splicing of that protein occurs ________. A) following translation B) between transcription and translation C) during transcription D) prior to transcription
A
When a repressor binds to the operator site on the DNA it normally ________. A) inhibits the initiation of transcription B) reduces the rate of transcription C) terminates transcription that has already been initiated D) has no effect on transcription
A
When does a cell regulate gene expression? A) Pretranscription through posttranslation B) Posttranscription through posttranslation C) Pretranscription through pretranslation D) Posttranscription through pretranslation
A
Which enzyme is a topoisomerase? A) DNA gyrase B) DNA ligase C) DNA polymerase I D) DNA polymerase III
A
Which is true regarding translation in bacteria? A) Translation begins with formation of the 30S initiation complex. B) Translation ends when the Shine-Dalgarno sequence is reached. C) The 70S ribosome is composed of a 20S and 50S subunit. D) All of the choices are correct.
A
Which modification of the terminator region of a gene would specifically prevent rho-independent termination? A) Change in the adenine-rich sequence of nucleotides of the terminator region. B) Change in the adenine-thymine sequence of the Pribnow box. C) Change in the sequence that encodes the mRNA leader. D) Change in the rut binding site.
A
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.
A
Which of the following events occurs initially when Escherichia coli cells are in a gradient of a chemorepellent? A) CheA autophosphorylates B) Flagella rotate clockwise C) Cells tumble D) CheY is phosphorylated
A
Which of the following is NOT a pyrimidine? A) Adenine B) Cytosine C) Thymine D) Uracil
A
Which of the following is an example of gene regulation at the posttranslational level? A) Alteration of protein structure B) Early termination of an mRNA transcript C) Initiation of protein synthesis D) Prevention of RNA synthesis
A
Which of the following is common to both factor-dependent and factor-independent transcription termination? A) Both types of termination occur following a pause by the polymerase. B) Both types of termination are associated with rho termination factor. C) Both types of termination involve NusA protein. D) None of the choices are correct.
A
Which of the following is not a termination codon? A) AUG B) UAA C) UAG D) UGA
A
Which of the following is not present in DNA? A) Alpha carbon B) 5'-carbon C) Minor groove D) 3'-hydroxyl E) Double helix
A
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.
A
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.
A
Which of the following statements best explains why microbial geneticists initially focused on regulation of gene expression at the transcriptional, rather than the translational, level? A) By regulating the first step of protein synthesis, cells conserve the greatest amount of energy. B) The process of transcription was best understood by researchers at the time. C) Cellular regulation of transcription is common to all prokaryotic cells. D) The process of synthesizing an mRNA transcript is much less complex than translation of mRNA into protein.
A
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
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.
A
Which set of codons terminate transcription in most organisms? A) UGA, UAG, UAA B) AGU, UAG, UAA C) ACT, TAC, ATT D) TGA, TAG, TAA
A
Which statement best describes the mechanism(s) of posttranslational regulation of gene expression? A) Allosteric regulation following transcription of mRNA occurs in many biosynthetic pathways. B) Protein synthesis is often repressed by feedback or noncompetitive inhibition. C) Covalent modification of newly synthesized proteins generally has no marked effect on protein function. D) Once a protein is synthesized, there is little to no postranslational modification.
A
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.
A
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.
A
While examining the sequence of nucleotides in the replicon region of bacterial DNA, you note an abundance of adenine and thymine base pairs. This leads you to conclude that this particular section of the DNA must be the ________. A) oriC site B) Pribnow box C) Shine-Dalgarno sequence D) ter site
A
Who first demonstrated transformation using mice and two strains of Streptococcus pneumoniae? A) Griffith B) Hershey and Chase C) Avery, McCarty, and MacLeod D) Watson and Crick E) Jacob and Monod
A
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 are correct.
A
Why did scientists originally believe that proteins, rather than DNA, were the molecules that directed protein synthesis? A) Proteins were the more complex molecules in which genetic information could be stored. B) Proteins were more likely to have catalytic properties for synthesis reactions. C) Proteins were the same types of molecules as those that were being synthesized. D) At the time, more was known about the structure of proteins than that of DNA.
A
You and a classmate are discussing early experiments in genetics, and you state that Avery, MacLeod, and McCarty provided the first evidence that DNA carries genetic information. Your classmate argues that Griffith was the first to demonstrate this. Which statement best defends your argument? A) Although Griffith first demonstrated transformation, Avery, MacLeod, and McCarty provided evidence that DNA rather than protein or RNA was the transforming agent. B) Avery, MacLeod, and McCarty worked with purified DNA extracts while Griffith worked with bacterial strains. C) Enzymes were used in the experiments carried out by Avery, MacLeod, and McCarty while Griffith transformed cells chemically or by using heat. D) Because Avery, MacLeod, and McCarty did their experiments after those done by Griffith, they had much more information regarding the structure and function of DNA. E) DNA used by Avery, MacLeod and McCarty was extracted solely from transformed strains of pneumococci, while Griffith used native pneumococcal strains.
A
________ alter repressor proteins thereby increasing the rate of transcription initiation. A) Inducers B) Corepressors C) Effectors D) Modulators
A
________ is used to control transcription of some anabolic pathways involved in amino acid biosynthesis. A) Attenuation B) Catabolite repression C) Induction D) All of the choices are correct.
A
Aminoacyl-tRNA synthetases catalyze covalent addition of ________ ________ to tRNAs.
AMINO ACIDS
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.
B
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 are correct.
B
A change in genotype, but not in phenotype, is most likely due to ________. A) a nonsense mutation at the beginning of a gene B) a point mutation in the third position of a DNA triplet C) a mutation that leads to a frameshift in the middle of a gene D) thymine dimer formation in the coding region of a gene
B
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
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.
B
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.
B
In general, riboswitches regulate in Gram-negative bacteria such as Escherichia and in Gram-positive bacteria such as Bacillus. A) transcription; translation B) translation; transcription C) replication; translation D) transcription; replication
B
In order to add a single amino acid to a growing polypeptide chain, a total of ________ molecules or ATP of GTP are utilized. A) two B) three C) four D) six
B
In two component regulatory systems, the response regulator typically receives a(n) ________ from the sensor kinase when it has been activated. A) pyruvate group B) phosphoryl group C) acetyl group D) methyl group
B
Plasmids that have genes that decrease bacterial susceptibility to antibiotics are called ________ factors. A) col B) resistance C) virulence D) metabolic
B
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.
B
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.
B
The Y-shaped part of the DNA molecule where the actual replication process occurs is called the replication ________. A) tongue B) fork C) junction D) splice
B
The ________ reaction sequentially links adjacent amino acids into the growing polypeptide chain. A) dipeptidation B) transpeptidation C) peptidation D) propeptidation
B
The genetic code is said to be ________ because more than one codon will specify a particular amino acid. A) ambiguous B) degenerate C) multiplicative D) repetitious
B
The genetic information in DNA is divided into units called ________. A) proteins B) genes C) genotype D) phenotype
B
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
B
The portion of the tRNA molecule that binds to the codon on the mRNA is called the ________. A) c-codon B) anticodon C) complementary codon D) paracodon
B
The process by which the base sequence of all or a portion of a DNA molecule is used to direct the synthesis of an RNA molecule is called ________. A) replication B) transcription C) reverse transcription D) translation
B
The region at which the RNA polymerase binds is the ________ region. A) leader B) promoter C) coding D) trailer
B
The sensing of starvation that leads to sporulation in Bacillus subtilis is accomplished by a ________. A) small RNA B) sensor kinase C) response regulator D) quorum regulatory effector
B
The sensor kinase for the OmpF: OmpC two-component regulatory system is ________. A) the OmpK protein B) the EnvZ protein C) the MicF RNA D) None of the choices are correct.
B
The site on the DNA to which a repressor protein binds is the ________. A) operon B) operator C) promoter D) regulator
B
The strand of DNA for a particular gene that is copied by the RNA polymerase to form mRNA is called the ________ strand. A) leading B) template C) transcription D) copy
B
What term describes a set of genes that is controlled by a common regulatory protein? A) Codon B) Regulon C) Transcription D) Kinase
B
When RNA polymerase catalyzes the addition of a nucleotide to a growing mRNA chain, a byproduct of this reaction is ________. A) phosphate B) pyrophosphate C) orthophosphate D) water
B
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
When an F plasmid integrates into the host chromosome, the strain is referred to as ________. A) F+ B) Hfr C) F' D) F−
B
When the catabolite activator protein binds to its binding site in DNA, it ________. A) displaces repressors B) bends the DNA C) promotes the assembly of other transcription factors at the promoter D) eliminates the need for a sigma factor on the part of RNA polymerase
B
Which is false regarding the two-component regulatory system in bacteria? A) The system involves a sensor kinase and a response regulator. B) The sensor kinase is phosphorylated by the response regulator when the extracellular environment changes. C) Regulation of OmpF and OmpC porin proteins in E. coli is modulated by this type of system. D) One part of the system is exposed to the external cellular environment while another part is exposed to the cytoplasm.
B
Which of the following is not a regulatory mechanism used to control the tryptophan operon in Escherichia coli? A) Repression B) Catabolite repression C) Attenuation D) All of the choices are correct.
B
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
While standard two-component regulatory systems typically act to control gene transcription, phosphorelay systems can act either to control gene transcription or to control . A) translation B) protein activity C) DNA replication D) All of the choices are correct.
B
________ activate repressor proteins, thereby decreasing the synthesis of certain enzymes. A) Inducers B) Corepressors C) Effectors D) Modulators
B
________ 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
________ molecules deliver amino acids to ribosomes during translation. A) Messenger RNA (mRNA) B) Transfer RNA (tRNA) C) Ribosomal RNA (rRNA) D) Heterogeneous nuclear RNA (hnRNA)
B
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
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.
C
By definition, if the DNA of a cell undergoes a spontaneous mutation, is was NOT due to ________. A) errors in DNA replication B) insertion of transposons C) exposure to radiation D) spontaneous depurination of nucleotides
C
Complete transfer in an Hfr × F− mating takes approximately ________ minutes. A) 20 B) 50 C) 100 D) 200
C
During replication, which enzyme unwinds the two strands of the DNA molecule from one another? A) Ligases B) Unwindases C) Helicases D) Primases
C
During the stringent response, ppGpp-regulated genes for amino acid biosynthesis have a(n) _________ promoter, thus forming a ________ open initiation complex. A) GC-rich; more stable B) GC-rich; less stable C) AT-rich; more stable D) AT-rich; less stable
C
Each chromosome has one or more ________ site(s) where replication begins. A) promoter B) replicon C) origin D) bifurcate
C
Enzymes that are expressed at a constant level all the time are said to be ________. A) inducible B) repressible C) constitutive D) attenuated
C
Guanine tetraphosphate (ppGpp) is associated with which process? A) Spore formation in Bacillus B) Chemiosmosis in Paracoccus C) Stringent response in Escherichia D) Quorum sensing in Vibrio
C
How many different termination codons are used in translation? A) One B) Two C) Three D) Four
C
If a region of DNA contained numerous mismatches due to a modifying agent that caused methylation of guanine, which of the following mutagens is most likely the cause? A) A deaminating base such as nitrous oxide B) An intercalating agent such as acridine orange C) A DNA modifier such as an alkylating agent D) Ionizing energy such as gamma radiation
C
In some circumstances, when two different carbon sources are available, growth will occur first using one carbon source, then after a short lag period, growth will resume using the second carbon source. This process is called ________ growth. A) alternating B) bimorphic C) diauxic D) dimorphic
C
Key sequences exist within promoters, which vary somewhat among various promoters but are sufficiently constant that they can be represented by a sequence of bases most often found at each position. These representations are called ________ sequences. A) convergence B) idealized C) consensus D) common
C
Lethal mutations can be recovered in bacteria if they are ________. A) dominant B) active C) conditional D) None of the choices are correct.
C
Microbial strains that can grow on minimal medium are called ________. A) autotrophs B) auxotrophs C) prototrophs D) minitrophs
C
Most E. coli antisense RNAs work with a protein called ________ to regulate their target mRNAs. A) CAP B) MicF C) Hfq D) None of the choices are correct.
C
Mutations that result in the death of an organism when expressed are called ________ mutations. A) dominant B) recessive C) lethal D) conditional
C
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.
C
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.
C
The E. coli lac operon has ________ operator sequences. A) one B) two C) three D) four
C
The Pribnow box of E. coli ________. A) is centered approximately 35 bp upstream of the start site of transcription B) is centered between 7 and 13 bp upstream of the start codon C) is centered approximately 10 bp upstream of the start site of transcription D) is located at the site of addition of poly (A) in eukaryotic mRNAs
C
The ________ is a factor-independent termination site found in the leader region of certain operons, which, under the influence of ribosome behavior, controls the continued transcription of that operon. A) modulator B) operator C) attenuator D) terminator
C
Transition mutations can result from ________. 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
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.
C
Which of the following is not a complementary base pair found in DNA molecules? A) Adenine-thymine B) Guanine-cytosine C) Adenine-uracil D) All of the choices are correct.
C
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.
C
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
Which of the following nitrogenous bases is usually found in RNA but not in DNA? A) Adenine B) Thymine C) Uracil D) Guanine
C
Which was common to experiments done by Avery and colleagues as well as Hershey and Chase? A) Radioactive DNA B) Virulent bacteriophage C) Bacterial cells D) Radioactive protein E) Escherichia coli
C
With the E. coli trp operon where both repression and attenuation occur, the extent of regulation achieved by repression is ________ the extent of regulation achieved by attenuation. A) the same as B) less than C) greater than D) Repression is not used in the regulation of the E. coli trp operon.
C
60) Cell-to-cell communication by quorum sensing has been shown to be important in the regulation of genes needed for ________. A) virulence B) biofilm production C) plasmid transfer D) All of the choices are correct.
D
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
D
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.
D
During the early stages of sporulation in Bacillus subtilis, ________ is active in the forespore and ________ is active in the mother cell. A) σE; σF B) σK; σF C) σF; σK D) σF; σE
D
During translation elongation, which event happens last? A) A tRNA carrying an amino acid binds to the A site. B) A peptide bond forms. C) A tRNA molecule translocates from the A site to the P site. D) A tRNA molecule translocates from the P site to the E site.
D
Following an F+ × F− mating, the donor is ________ and the recipient is ________. A) F+; F− B) F−; F+ C) F−; F− D) F+; F+
D
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.
D
It has been observed that when the sugar source changes in a growth medium, the growth rate of yeast vary widely in response. Some strains of yeast are slow to induce catabolic operons while other strains quickly synthesize proteins to process the new sugar. What might be one explanation for this difference in the growth rate of the strains? A) Different sugars can act as effector or repressor molecules in various strains, promoting or inhibiting transcription of genes depending on the type of sugar present. B) Operons for anabolic pathways are controlled by many global regulatory mechanisms, and different sugars can favor initiation of different pathways depending on the strain of yeast. C) All of the choices are correct. D) Catabolic repression strategies of operons for using different sugars may vary among strains, thereby favoring initiation of transcription in one strain over another depending on the sugar.
D
Over twisting or under twisting of helical DNA generates ________. A) hypertwists B) hypotwists C) hypercoils D) supercoils
D
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.
D
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.
D
The energy needed for protein synthesis is provided by the hydrolysis of ________. A) ATP B) GTP C) UTP D) ATP and GTP E) ATP and UTP
D
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
The process by which the base sequence of an RNA molecule is used to direct the synthesis of a protein is called ________. A) replication B) transcription C) reverse transcription D) translation
D
Transfer of genetic information via direct cell-cell contact is called ________. A) transformation B) transduction C) transfection D) conjugation
D
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
D
What is the key factor determining whether or not attenuation will occur when transcription of the E. coli trp operon has been initiated? A) The activity level of adenyl cyclase B) The trp operon repressor C) The level of tryptophan in the environment D) The level of trp-tRNA that is charged with tryptophan
D
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.
D
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 are correct.
D
Which of the following is in the coding region of a gene? A) Promoter B) Leader C) Trailer D) None of the choices are correct.
D
Which of the following is true about the structure of DNA? A) Purine and pyrimidine bases are attached to the 1'-carbon of the deoxyribose sugars. B) Nucleotides are joined by phosphodiester bonds. C) Adjacent nucleotides are stacked on top of each other, one base pair every 0.34 nm. D) All of the choices are correct.
D
Which of the following mutagens is most different than the others in terms of its effect on DNA? A) Acridine orange B) Intercalating agent C) Planar mutagen that inserts between stacked bases D) Base analogue
D
Which type(s) of mutation might lead to a threonine auxotrophic revertant? A) Base substitution B) Missense mutation C) Point mutation D) All of the choices are correct.
D
Which of the following statements is false regarding the consequences of horizontal gene transfer? A) Horizontal gene transfer is the main mechanism that drives the evolution of microorganisms. B) Horizontal gene transfer allows microbes to better survive environmental stresses such as UV radiation by replacing their own damaged DNA with intact DNA from another organism. C) Genetic changes resulting from horizontal gene transfer affects the virulence of bacteria when pathogenicity islands are transferred between organisms. D) Microbes can expand their ecological niche when horizontal gene transfer bestows beneficial traits such as antibiotic resistance. E) Horizontal gene transfer allows the donor DNA to self replicate, simultaneously repressing reproduction in the recipient.
E
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.
F
DNA replication is a complex process, and, as a result, the frequency of error is quite high.
F
During DNA replication, deoxyribonucleosides are added to the 5' end of Okazaki fragments and to the 3' end of the leading strand.
F
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.
F
Helix-turn-helix and zinc fingers are secondary structural motifs in DNA and RNA, respectively.
F
Hershey and Chase used 35S-labeled protein and 32P-labeled DNA of T2 bacteriophage to infect cells of Streptococcus pneumoniae bacteria.
F
In Escherichia coli, if σ70 is not bound to RNA polymerase core enzyme, active transcription of the gene is not occurring
F
In an F+ × F− mating, all or part of the host chromosome usually is transferred to the recipient.
F
In the presence of both glucose and lactose, the lactose repressor is not bound to the operator and the genes of the lactose operon are expressed.
F
Membrane vesicles are used to transport material between cells as an alternative to protein secretion systems. Regardless of the nature of the bacterial envelope, all vesicles are produced by the same mechanism.
F
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.
F
Prior to secretion, Gram-negative bacterial proteins are translocated across one membrane while Gram-positive proteins are translocated across two membranes.
F
Scientists first focused on gene regulation at the level of translation, rather than transcription, because more was known about protein than nucleic acids at the time.
F
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.
F
The THI-element is part of the operon that controls synthesis of thymine in mRNA.
F
The binding of arabinose to the AraC protein allows it to form a loop in the DNA upstream of the ara operon promoter.
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+.
F
The inducer for the E. coli lac operon is allolactose produced by the action of permease on lactose.
F
The molecular weights of a nucleic acid and an amino acid are approximately the same.
F
The number of N and C termini in a polypeptide chain is equal to the number of amino acids that make up that chain.
F
The stop codons are translated codons; that is, they specify amino acids to be inserted into the last position of a growing polypeptide chain.
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.
F
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.
F
Transposable elements have been found only in bacteria and do not appear to play a major role in eukaryotes.
F
Two-component signal transduction systems are found in the Bacteria, but not in Archaea.
F
When tryptophan levels in a cell are low, a cell will stall transcription but continue translation of the tryptophan operon.
F
________ are physical or chemical agents that cause mutation.
MUTAGENS
________ mutations affect only a single base pair in a gene.
POINT
________ 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
A collection of genes or operons controlled by a common regulatory protein is called a(n) ________.
REGULON
Host ________ is the process by which some cells are able to degrade an exogenote.
RESTRICTION
A consensus sequence in the untranslated leader sequence of a prokaryotic mRNA, which serves as a ribosome binding site is called the ________ - ________ sequence.
SHINE DELGARNO
A bacterial cell that secretes proteins by types II and V systems is most likely Gram-negative.
T
Bacteria with DNA described as having "hairpin ends with inverted repeats" must not have circular chromosomes
T
Bacterial chromosomes, unlike eukaryotic chromosomes, often consist of a single replicon.
T
By using enzymes that destroyed DNA, RNA, or protein, Avery and colleagues were able to determine which of the three molecules was required to transform bacterial cells.
T
Catenanes are interlocked chromosomes that form during the termination stage of DNA replication.
T
Competency has been observed in only a limited number of species in nature, but we have found ways to induce the process upon other species in the laboratory.
T
DNA polymerase and aminoacyl-tRNA synthase are similar in that both have proofreading ability, but differ in the substrates that they act upon.
T
During regulation by attenuation in the trp operon, if the pause and terminator loops form in mRNA, transcription is uncoupled to translation and protein synthesis is not occurring.
T
During tryptophan synthesis in Escherichia coli, the 1:2 attenuator sequence of mRNA is called the pause loop.
T
Gene regulation during sporulation in Bacillus subtilis involves both temporal and spatial control.
T
Genes for antibiotic resistance can be found in antibiotic-producing bacteria as well as in non-antibiotic-producing bacteria
T
If 5-bromouracil was added to a culture of actively dividing bacterial cells, resulting mutations could eventually become a stable part of the cellular genome.
T
If the DNA of a new discovered organism exhibits genes that are arranged as operons and lacks intron sequences, the hypothesis that this organism is bacterial rather than mammalian would be supported by the evidence.
T
In an Hfr × F− mating, the conjugation bridge usually breaks before chromosomal transfer is complete. Therefore, the recipient remains F−.
T
In the mechanics of conjugation, exclusive of gene transfer, Hfr and F+ strains behave the same.
T
One way to regulate gene expression is through the production of different sigma factors. These cause RNA polymerase to bind to different sets of promoters, thereby altering the pattern of gene expression.
T
Signal recognition particles (SRPs) are associated with the Sec translocation system.
T
Small RNAs that regulate translation by binding to the leader region of mRNAs are called antisense RNAs.
T
The B form of the DNA double helix contains a wider major groove and a narrower minor groove because the two polynucleotide strands are not positioned directly opposite one another in the helical cylinder.
T
The Tat and Sec pathways are protein translocation systems.
T
The first amino acid in a bacterial protein is N-formylmethionine; the presence of the formyl group makes it the initiator amino acid.
T
The genes that code for tRNA often contain multiple tRNA sequences controlled by a single promoter, requiring posttranscriptional modification by ribonucleases.
T
The noncoding sequences located between the start codon and the stop codon in interrupted genes are called introns.
T
This initiator tRNA of the bacterium Escherichia is a modified form of the initiator tRNA used by the yeast Saccharomyces.
T
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.
T
) When arabinose is present in the environment, the AraC protein acts as a(n) ________ for the E. coli ara operon.
activator
If you wished to study the SOS response in Escherichia coli, which of the following experimental procedures could be used? A) Expose cells to nonionizing radiation for 20 minutes. B) Expose cells to ionizing radiation for 10 minutes. C) Transfer log phase cells from complete medium to thymine minimal medium. D) Inactivate genes that encode DNA polymerases. E) All of the choices are correct.
e
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.
less
