Ch. 6 8 9 10 quiz questions

According to the animation, to what genetic element does the RNA polymerase bind? A. The operator B. The promoter C. The repressor mRNA D. The repressor protein

B. The promoter

Which of the following best describes the effect of autoinducers as their concentration increases around bacterial cells? A. They bind to bacterial receptors. B. They alter bacterial gene expression. C. They form extracellular matrix. D. They induce bacterial cell growth.

B. They alter bacterial gene expression. - Autoinducers are signaling molecules that bacteria use for quorum sensing. As the concentration of autoinducers increases, more and more bacterial receptors are activated. At some threshold level, the activated receptors cause changes in bacterial gene expression. These changes contribute to biofilm development, and may trigger increased virulence.

What is the basic function of the lac operon? A. To code for enzymes involved in synthesizing lactose. B. To code for enzymes involved in catabolizing lactose. C. To produce lactose when none is present D. To produce glucose when none is available

B. To code for enzymes involved in catabolizing lactose.

A chemostat is continuous culture system that is designed to promote and prolong exponential growth and prevent bacteria from entering stationary phase. How might this work? A. Chemostats provide a continued source of fresh nutrients and remove wastes and dead bacterial cells. B. Chemostats promote the formation of endospores, which enable the long-term survival of the bacteria. C. Chemostats include growth-promoting agents that prolong microbial growth. D. Chemostats include detoxifying agents that inactivate growth-inhibiting toxins that develop during continued microbial growth.

A. Chemostats provide a continued source of fresh nutrients and remove wastes and dead bacterial cells.

When is the repressor protein transcribed? A. It is always transcribed. B. Only in the absence of tryptophan C. Only in the presence of tryptophan

A. It is always transcribed.

When performing phage typing to identify an unknown bacterium, you must have ________ in your possession. A. fluorescent molecules that will light up when bound to the DNA of the bacterium B. DNA that will hybridize to the DNA of the bacterium to be identified C. RNA that will hybridize to the RNA of the bacterium to be identified D. viruses that will specifically infect the bacterium you're trying to identify E. antiserum containing antibodies that will bind to the bacterium to be identified

D. viruses that will specifically infect the bacterium you're trying to identify

What is the inducer molecule in the lac operon? A. Glucose B. Galactose C. Allolactose D. Repressor proteins E. Lactose

Allolactose

In this activity, you will sort various groups of organisms into the correct domain. Organisms for Archaea, Bacteria, and Eukarya

Archaea: methanogens extreme halophiles hyperthermophiles Bacteria: cyanobacteria gram-positive bacteria proteobacteria Eukarya: fungi ciliates green algae slime molds

Why is the tryptophan operon turned off in the presence of tryptophan? A. Tryptophan is not an important amino acid for cells. B. Tryptophan can be used over and over again in the cell. C. Tryptophan binds to and activates the repressor proteins; the repressor proteins, in turn, bind to the operator, preventing transcription.

C. Tryptophan binds to and activates the repressor proteins; the repressor proteins, in turn, bind to the operator, preventing transcription.

In one hospital, Pseudomonas aeruginosa serotype 10 infected the biliary tract of 10 percent of 1300 patients who underwent gastrointestinal endoscopic procedures. After each use, endoscopes were washed with an automatic reprocessor that flushed detergent and glutaraldehyde through the endoscopes, followed by a tap water rinse. P. aeruginosa serotype 10 was not isolated from the detergent, glutaraldehyde, or tap water. What was the source of the infections? A. None of the answers is correct. B. contaminated disinfectant C. a biofilm in the reprocessor D. fecal contamination of the bile ducts E. bacterial cell walls in the water

C. a biofilm in the reprocessor

The area around and above the biofilm shown below is filled with an antibiotic. Of the four cells labeled in the biofilm, which would be exposed to the LOWEST concentration of antibiotics?

cell 4 - Antibiotic molecules move into a biofilm by diffusion. Cells near the surface of the biofilm or near a water channel are exposed to the highest concentrations of antibiotic. The matrix surrounding deeper layers of the biofilm acts as a barrier to antibiotic diffusion. The concentration of antibiotics therefore decreases as one goes deeper into the biofilm. Cells near the surface are easily killed off, but those in the deeper layers, like Cell 4, are less affected. This is one of the reasons biofilms are so hard to completely remove with antibiotic treatment.

In the figure, the closest ancestor for both species "a." and species "b." would be which of the following?

5

With which genetic region does the repressor protein interact? A. lacY B. The regulatory gene C. The operator region D. lacZ E. The promoter region

C. The operator region

How many pieces will EcoRI produce from the plasmid shown in the figure?

2

After a period of rapid growth (log phase), bacterial growth rates will slow and enter the stationary phase. The number of viable cells no longer increases, but instead stays constant. In this activity you will indicate the statements that correctly describe what is happening during stationary phase. (pick all that apply) A. The number of cells that are dying is balanced by the number of new cells that are being formed. B. The cells are dead; therefore, the number is staying constant. C. Harmful waste products may be accumulating. D. Cells are not increasing in number because they have not yet adjusted to the nutrient availability in the new media. E. The cells are likely running out of nutrients.

A, C, E - During the stationary phase, the number of viable cells does not increase and remains constant, or stationary. This phase begins as the nutrient supply is depleted and/or waste products begin to accumulate at a toxic level.

In addition to physical requirements, bacterial growth and multiplication also entails chemical requirements. Which of the following statements would accurately describe chemical requirements and conditions associated with growth in the Lake of the Ozarks environment? (pick all that apply) A. Fecal coliforms will need to acquire trace elements for growth in the lake environment. B. The lake environment will support only the growth of obligate anaerobes. C. Fecal coliforms will likely contain enzymes to counteract toxic oxygen forms. D. Fecal coliforms will not need organic growth factors to grow in the lake environment. E. The lake environment will support the growth of facultative anaerobes.

A, C, E - With chemical and physical requirements met, bacteria are able to replicate in their environment and potentially increase numbers enough to find or invade a new host.

Recombinant DNA techniques typically involve generating a clone. Why? A. Producing a clone generates many copies of the gene of interest. B. Recombining the clone produces the recombinant DNA. C. A clone is used to get the gene of interest into a suitable cell. D. A clone is generated when a cell takes up the vector.

A. Producing a clone generates many copies of the gene of interest. - In a strict sense, recombinant DNA (rDNA) is simply a DNA molecule that combines two or more sequences from different sources—for example, a plasmid from a bacterium, and the gene coding for insulin from a human. However, recombinant DNA techniques are typically used to produce more than just a single rDNA molecule. Usually the goal is to produce many copies of the gene—either to harvest those DNA copies, or to produce (and harvest) large amounts of the gene's protein product. In either case, once the vector is taken up by a bacterium, that bacterium is allowed to reproduce naturally. This produces a large number of identical cells—a clone—with each cell containing a copy of the gene of interest.

Which one of the following characteristics most reasonably indicates that two microorganisms are closely related? A. Their DNA can hybridize together. B. Both ferment lactose. C. Both normally live in clams. D. Both are cocci. E. Both are motile.

A. Their DNA can hybridize together.

Transformation is the transfer of DNA from a donor to a recipient cell A. as naked DNA in solution. B. by sexual reproduction. C. by cell-to-cell contact. D. by crossing over. E. by a bacteriophage.

A. as naked DNA in solution.

A base insertion or deletion in the translated region of the gene may lead to A. frameshift mutation. B. silent mutation. C. nonsense mutation. D. missense mutation.

A. frameshift mutation.

Quorum sensing affects biofilm development through control of __________. A. gene expression B. water channels C. bacterial growth D. bacterial attachment

A. gene expression - Quorum sensing is the process by which bacteria sense the density of nearby microorganisms. Bacteria respond to changes in this density of neighboring cells though changes in gene expression. These changes in gene expression lead to particular characteristics of the biofilm: matrix formation, water channels, and cooperative relationships with other bacterial species.

A mutation that affects the genotype of the organism but not the phenotype is called a A. silent mutation. B. frameshift mutation. C. nonsense mutation. D. missense mutation.

A. silent mutation.

Self-replicating DNA used to transmit a gene from one organism to another is a A. vector. B. clone. C. Southern blot. D. PCR. E. library.

A. vector.

Which of the following is NOT a characteristic of members of the Domain Archaea? A. They carry out unusual metabolic processes. B. They contain distinctive ribosomal RNA. C. They contain nuclei. D. They live in extreme environments.

C. They contain nuclei.

In the figure, which line best depicts a facultative anaerobe in the absence of O2?

B

The Lake of the Ozarks is a human-made lake, so it collects runoff from coal strip-mining, fertilizers, resort wastewaters, and septic drainages. The average lake temperature is between 10∘C and 21∘C. Consider the physical requirements for growth and multiplication that would allow fecal coliforms to "blossom" in the Lake of the Ozarks. Which of the following would accurately describe these organisms? (pick all that apply) A. Extremophiles B. Psychrophiles C. Hyperthermophiles D. Facultative halophiles E. Mesophiles

B, D, E - The bacterial growth process depends on the microorganism's ability to adapt to environmental conditions. Being able to grow to larger numbers increases the chances for survival and spread to new hosts. Requirements for growth have led us to develop descriptive terms for the organisms that refer to temperature range [Chapter 6, section 6-1], pH range [Chapter 6, section 6-2], and pressure range [Chapter 6, section 6-3].

The first cells were formed approximately __________ years ago. A. 3 million B. 3 billion C. 2 billion

B. 3 billion

What is the temperature used for the extension step? A. 60 °C B. 72 °C C. 94 °C

B. 72 °C

If cells are grown in media containing amino acids labeled with radioactive nitrogen (15N), most of the radioactivity will be found in the cells' A. DNA. B. DNA and proteins. C. phospholipids. D. proteins. E. DNA and phospholipids.

B. DNA and proteins.

How frequently do silent mutations occur? A. One out of every billion mutations B. One out of every three mutations C. Half of all mutations D. One out of every million mutations

B. One out of every three mutations

When the cell is NOT in the presence of tryptophan, A. structural genes are not transcribed. B. RNA polymerase can transcribe mRNA. C. the repressor proteins bind to the operator. D. the repressor proteins are active.

B. RNA polymerase can transcribe mRNA.

How do the strands separate during PCR? A. The cycling of the temperatures breaks the hydrogen bonds between the two strands. B. The high heat of the denaturation step breaks the hydrogen bonds between the two strands. C. The primers separate the strands during the annealing step. D. The DNA polymerase breaks the hydrogen bonds between the two strands.

B. The high heat of the denaturation step breaks the hydrogen bonds between the two strands.

What is a thermocycler? A. The name for the DNA primers used in a PCR reaction B. The machine that controls the heat of the reaction, cycling between the different temperatures of the different steps during PCR C. The process of cycling through the different temperatures of a PCR reaction 30 times D. The special DNA polymerase, used in a PCR reaction, that can tolerate the high temperatures

B. The machine that controls the heat of the reaction, cycling between the different temperatures of the different steps during PCR

Serological testing is based on the fact that A. antibodies cause the formation of antigens. B. antibodies react specifically with an antigen. C. bacteria clump together when mixed with any antibodies. D. all bacteria have the same antigens. E. the human body makes antibodies against bacteria.

B. antibodies react specifically with an antigen.

Bacteria naturally prefer company instead of solitude for growth. Examples of this kind of communal growth pattern can be found everywhere, from surfaces of the teeth and the intestines, to the surface of a slimy rock in the lake, to the thick floc that clogs water pipes. These examples of communal bacterial growth are known by what name? A. planktonic unit B. biofilm C. colony D. infectious unit

B. biofilm - Biofilms are a large collection of mixed populations of organisms that form a matrix of "slime" for protection and assemble a complex, coordinated, and functional community on a surface. Biofilms often provide a safe haven for bacterial growth, often among "friendly" microorganisms. The complex architecture of biofilms gives the cells benefits they would not have in an individual lifestyle as a planktonic cell. As such, biofilms can play an extremely important role in colonizing a host and leading to a disease state.

Cultures of the Lake of the Ozarks water samples were grown on enrichment media for identification. However, these organisms are present to some degree in all samples. An important question from a clinical perspective is whether or not there is a significant increase in the fecal coliform populations that would put people's health at risk. If you were part of the team investigating this outbreak, how would you best enumerate the fecal coliform threat? A. plate count culture B. filtration count culture C. direct microscopic counts D. serial dilution count culture

B. filtration count culture - This method will trap organisms and keep them on the surface of the filter. Transferring the organisms to a plate will then produce an accurate count. Fecal coliform bacteria were counted by direct filtration CFUs. Some of the samples taken at the beaches exceeded the recommended maximum levels established by the Environmental Protection Agency (EPA) for direct sampling: greater than 235 E. coli per 100 ml of water, or a geometric mean of greater than 126 E. coli per 100 ml of water. The beach samples were 178.2 E. coli per 100 ml and 1299.7 E. coli per 100 ml, with a geometric mean of 173.2 E. coli per 100 ml.

If you knew the sequence of nucleotides within a gene, which one of the following could you determine with the most accuracy? A. the secondary structure of the protein B. the primary structure of the protein C. the tertiary structure of the protein D. the quaternary structure of the protein E. The answer cannot be determined based on the information provided.

B. the primary structure of the protein

When the cell is not in the presence of lactose, A. no transcription of the regulatory genes occurs. B. the repressor proteins bind to the operator. C. transcription of the structural genes occurs. D. the repressor proteins are inactivated

B. the repressor proteins bind to the operator.

Each of the three graphs shown below includes data collected during exponential growth of a species of bacteria grown in three different growth conditions. Which growth condition resulted in the longest generation time?

C - The graph of exponential growth under growth condition C illustrates the slowest rate of growth and, thus, the longest generation time.

A unicellular, photosynthetic nucleated cell would belong to which domain? A. Archaea B. Bacteria C. Eukarya

C. Eukarya

According to the animation, how do the repressor proteins block the transcription of the structural genes? A. It binds to the repressor gene when activated. B. It binds to the repressor gene when deactivated. C. It binds to the operator when activated. D. It binds to the promoter when activated. E. It binds to the promoter when deactivated. F. It binds to the repressor when deactivated.

C. It binds to the operator when activated.

Sampling lake water for microscopic organisms is not as easy as it sounds when you want to both count and identify species. In a given water sample, your bacteria of choice can be rare or difficult to culture, particularly given the mixture of bacteria in a biofilm. Which of the following culture media would be best for growing fecal coliforms when they are relatively less abundant than other bacteria in the lake? A. basic culture medium B. complex culture medium C. enrichment culture medium D. anaerobic culture medium

C. enrichment culture medium - Growth of microorganisms for identification is not a trivial exercise. To accurately and efficiently grow bacteria in culture, you must consider the bacteria's relative abundance, metabolic and chemical needs, and best growth conditions, as well as the cost and overall goals of the experiment. Enrichment culture medium is a good choice for environmental samples whose desired populations are low compared to the rest of the microbes present. From a sample of large numbers of organisms, complex medium favors the growth of only certain organisms.

This activity asks you to consider various methods of counting or estimating the size of bacterial populations and to select the method that will provide the most accurate data for plotting a bacterial growth curve. Which of the following methods would be most appropriate for gathering data to plot a bacterial growth curve throughout the four phases? A. direct microscopic count B. Any of these methods will provide reliable data for plotting a growth curve. C. plate count D. electronic cell counter E. indirect estimate based on turbidity

C. plate count - A plate count will provide the number of living cells. These data are most appropriate for generating a plot of a bacterial growth curve.

What is the sequence of the temperatures of a typical PCR reaction? A. 94 °C, 72 °C, 60 °C B. 72 °C, 60 °C, 94 °C C. 72 °C, 94 °C, 60 °C D. 94 °C, 60 °C, 72 °C E. 60 °C, 72 °C, 94 °C

D. 94 °C, 60 °C, 72 °C

Which enzyme catalyzes the reaction: O2- + O2- + 2H+ → H2O2 + O2? A. catalase B. oxidase C. peroxidase D. superoxide dismutase

D. superoxide dismutase

Which of the following best describes how recombinant DNA technology currently helps patients who do NOT produce adequate amounts of growth hormone (hGH)—a condition that otherwise leads to stunted growth? A. Recombinant vectors are used to stimulate hGH production in these patients. B. Recombinant vectors now produce hGH. C. Bacteria now produce rDNA coding for hGH. D. Bacteria now produce hGH.

D. Bacteria now produce hGH. - To achieve normal growth, these patients need regular injections of hGH (a protein). Before rDNA technology was developed, hGH could be obtained only from the brains of human cadavers, which was both expensive and unsafe. But once the gene for hGH was inserted into bacteria, all of that changed. These bacteria now produce hGH protein that is harvested and purified by pharmaceutical companies. This represents a safe and (relatively) inexpensive source of hGH that has helped thousands of patients.

Which of the following best describes why a vector is used in genetic modification procedures? A. The clone must be able to produce proteins from the rDNA containing the gene of interest. B. The gene of interest must be isolated from adjacent genes. C. The vector ensures that the clone remains pure. D. Cells usually won't copy an isolated gene sequence.

D. Cells usually won't copy an isolated gene sequence. - Vectors, sometimes called gene-cloning vectors, are necessary vehicles for inserting genes of interest into bacteria. A DNA sequence from a human, by itself, won't do much if taken up by a bacterium. DNA molecules with exposed ends (i.e., noncircular) are degraded by bacterial enzymes. Even if the sequence persists long enough to be translated, it still won't be copied because it lacks the necessary sequence to initiate replication. Incorporating the human sequence into a vector provides a means for that sequence to be copied within the bacterium. The recombinant vector copies are then passed on to subsequent daughter cells that make up the clone.

What is considered to be the average natural mutation rate that occurs during DNA replication? A. One in every million nucleotides replicated. B. One in every trillion nucleotides replicated. C. One in every ten thousand nucleotides replicated. D. One in every billion nucleotides replicated.

D. One in every billion nucleotides replicated.

When bacteria are inoculated into a new sterile nutrient broth, their numbers don't begin to increase immediately. Instead, there is a lag phase that may last for an hour or even several days. Why don't bacterial numbers increase immediately? A. The bacteria have to establish a biofilm before their numbers can increase. B. There are not enough nutrients for the bacteria to grow, and growth is delayed until there are some dead cells to cannibalize. C. The medium contains inhibitors that prohibit rapid growth of the bacteria, and these must be inactivated before bacterial numbers will increase. D. The bacteria must adjust to the nutrient content in the new medium, synthesizing necessary amino acids, growth factors, and enzymes.

D. The bacteria must adjust to the nutrient content in the new medium, synthesizing necessary amino acids, growth factors, and enzymes. - A new medium may not have the same nutrients that were available in the medium from which an inoculum was taken. The bacteria may have to synthesize different amino acids, growth factors, or enzymes to enable them to grow in this new medium. Once those are synthesized, the growth rate is likely to increase, and the cells will move into log (exponential) growth phase.

What is the overall function of the trp operon? A. To control the production of repressor proteins B. To block RNA polymerase from the structural genes C. To always make sure the operator is being bound to repressor proteins D. To ensure that the cell has a supply of tryptophan at all times

D. To ensure that the cell has a supply of tryptophan at all times

Which of the following techniques could be used to identify antibodies produced by a patient? A. FAME B. Southern blotting C. FISH D. Western blotting

D. Western blotting When Western blotting is used for identification purposes, proteins from a known organism are used to determine whether a patient's serum contains antibodies.

Which of the following best describes a clone in the context of genetic modification procedures? A. an identical copy of the gene of interest B. a vector, once it contains a copy of the gene of interest C. a cell that is genetically identical to its parent D. a culture of genetically identical cells

D. a culture of genetically identical cells - clone (as a noun) refers to a culture of identical cells. For example, a clone might refer to a culture of bacterial cells that contain a particular recombinant DNA plasmid, as in, "This is our clone of human insulin." Perhaps confusingly, the word clone is also used as a verb to describe the overall process of using recombinant DNA techniques to create numerous copies of a gene—for example, "The gene for human growth hormone has been cloned."

During which growth phase will gram-positive bacteria be most susceptible to penicillin? A. death phase B. lag phase C. stationary phase D. log phase E. The culture is equally susceptible during all phases.

D. log phase

A base substitution that changes a codon coding for an amino acid to a stop codon is called a A. frameshift mutation. B. missense mutation. C. silent mutation. D. nonsense mutation.

D. nonsense mutation.

Which of the following pairs of microbe classification terms and optimal growth temperatures is mismatched? A. hyperthermophiles - growth at greater than 80°C B. mesophile - growth at 25-40°C C. psychrotroph - growth at 20-30°C D. psychrophile - growth at 15°C E. thermophile - growth at 37°C

E. thermophile - growth at 37°C

A broth medium has been inoculated, and microbial numbers will be counted periodically to generate a bacterial growth curve. At 2 hours after inoculation, the culture has progressed through lag phase and is now in log phase. At this point, the population size is 1 million cells. The generation time is 30 minutes. Assuming the continuation of log growth, how many cells would there be at 2 hours of growth in log phase? A. 2 million B. 32 million C. 4 million D. 8 million E. 16 million

E. 16 million - There would be approximately 16 million cells. In the 2-hour interval of log growth, there are four 30-minute generations. This is four doublings of the 1 million organisms present at hour 2.1 million cells x 24 = 16 million cells

Which of the following statements is FALSE? A. Multiple replication forks are possible on a bacterial chromosome. B. The leading strand of DNA is made continuously. C. DNA polymerase joins nucleotides in one direction (5' to 3') only. D. The lagging strand of DNA is started by an RNA primer. E. DNA replication proceeds in only one direction around the bacterial chromosome.

E. DNA replication proceeds in only one direction around the bacterial chromosome.

The term aerotolerant anaerobe refers to an organism that A. requires less oxygen than is present in air. B. is killed by oxygen. C. requires more oxygen than is present in air. D. tolerates normal atmospheric nitrogen gas levels. E. does not use oxygen but tolerates it.

E. does not use oxygen but tolerates it.

In the figure, the antibiotic chloramphenicol binds the 50S large subunit of a ribosome as shown (the light gray area is the large subunit, while the black shape is the drug). From this information you can conclude that chloramphenicol A. prevents translation in eukaryotes. B. prevents transcription in eukaryotes. C. prevents transcription in prokaryotes. D. prevents mRNA-ribosome binding. E. prevents translation in prokaryotes.

E. prevents translation in prokaryotes.