MCB17

24 July 2022
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70 test answers

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question
A (n) __________ vector contains promoters that result in high-level transcription of the gene cloned within a multicloning site.
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expression
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Which of the following components of PCR ensures amplification of the target DNA sequence only, despite the presence of many other DNA sequences?
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primers
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During the investigation of a convenience store robbery, witnesses report that the perpetrator exited through a main entry door without wearing gloves. The police are holding a prime suspect in custody while samples from the door are collected and analyzed for a DNA match. Since the door was handled by many people before the robbery, how will the forensics department distinguish the suspect's DNA from the DNA of others using PCR?
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Sequence-specific primers to the suspect's DNA will be used for PCR amplification.
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Some plasmid vectors have incorporated the regulatory sequences of the lactose operon so that the expression of the recombinant gene can be induced at the appropriate time.
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TRUE
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When a eukaryotic gene is expressed in a bacterium, the eukaryotic regulatory sequences should be maintained in order to achieve maximum expression of the gene.
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false
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A molecular biologist is interested in purify a recombinant protein by His-tagging, but the protein and vector both lack histidine residues. In this case, the molecular biologist could use which of the following technique(s) to acheive purification?
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A. Add a 6xHis-tag to the C-terminus of the protein. B. Add a series of histidine residues to the N-terminus of the protein. C. Amplify the histidine-encoding sequence by PCR and add it to the gene of interest. D. All of the choices are correct.
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Which situation(s) might warrant the removal of a histidine tag when purifying a recombinant protein?
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Histidine residues inhibit protein folding, thereby decreasing the functionality of the protein.
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Which is most analogous to the role of GFP in recombinant DNA technology?
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Using dyes to stain and detect bacteria under light microscopy from the sputum of a patient diagnosed with tuberculosis.
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As a newly hired molecular biologist for a company that produces genetically modified seeds, your first project is to ensure that a GM cotton plant carrying a bacterial insecticide gene is expressed in tissues of seedlings as well as mature plants. To better understand regulation of the gene, you decide to use________ GFP fusion to detect activity of the promoter and also use_______ GFP fusion to determine the location of the protein in plants tissues at various stages of growth.
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transcriptional; translational
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A genomic __________ is a sufficiently large collection of recombinant DNA molecules in which the inserted sequences together represent the entire genome of an organism.
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library
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Which of the following terms is most closely related to genetic complementation?
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Phenotypic rescue
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Promoters for genes that code for proteins can be isolated from a cDNA library.
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false
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Which of the following techniques exemplifies phenotypic rescue in a host cell?
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Introducing a genomic library from a cell that produces a particular gene product into a mutant host cell auxotroph that cannot synthesize the product.
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A microbial ecologist who is interested in studying how gene expression is influenced by different species of bacteria in a biofilm would most likely find a metagenomic library more useful than a genomic library.
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true
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In _____________, cells are mixed with recombinant DNA and exposed to a brief pulse of high-voltage electricity to cause the membrane to become permeable and allow the uptake of DNA from its environment.
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electroporation
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Which of the following bacterial hosts would should be used to avoid degradation of DNA that is introduced via a cloning vector?
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Escherichia coli that lack endonucleases
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A microbiologist would like to use a noncompetent genus of streptococcal bacteria, Enterococcus faecalis, as a cloning host to express genes from Streptococcus pneumoniae, which is naturally competent. Is this possible?
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Yes; electroporation or chemical transformation can be used to make Enterococcus competent, and then genes from Streptococcus can be introduced via a cloning vector.
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Regardless of the exact approach taken to recombinant DNA technology, one of the keys to successful cloning is choosing the right vector.
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true
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Which cloning vector should be used to express a 500-kb DNA fragment in Saccharomyces cerevisiae?
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YAC
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You and a friend are student assistants in a research laboratory that investigates the anti-cancer properties of proteins isolated from marine organisms. Your friend mentions that she is using a BAC vector to insert shark DNA into Escherichia coli, but after repeated attempts, has found that the bacterial cells fail to synthesize the encoded protein. What is your advice?
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If the shark DNA is unmodified, it contains introns that are not recognized by bacteria, therefore protein synthesis will not occur.
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Which of the following is not true of cloning vectors?
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They contain at least two replication origins.
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Which of the following can be used as vectors for cloning DNA fragments?
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A. plasmids B. cosmids C. bacteriophages D. All of the choices are correct.
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Plasmid cloning vector DNA is usually introduced into bacterial hosts by
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transformation
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Plasmid vectors often contain __________ genes that can be used to screen for recombinants.
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antibiotic resistance
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A DNA molecule used to carry a foreign gene into a host organism is called a
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vector
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Antibiotics incorporated into the culture medium can
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select against organisms that have not incorporated the plasmid.
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A (n) __________ vector is a plasmid that can be replicated in several different organisms because it has at least one origin of replication that will function in each host.
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shuttle
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___________ is a bacterial plasmid vector.
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pUC19
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Which of the following is not part of a yeast artificial chromosome (YAC)?
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the F factor
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Which of the following types of cloning vector can carry the largest amount of foreign DNA?
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bacterial artificial chromosome
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Cosmids are plasmids that can be packaged into capsids of the bacteriophage lambda; therefore, they can be transmitted like phages, but they can exist and replicate in a cell like plasmids.
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true
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Transposons are frequently used as cloning vectors.
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false
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Cosmids are so named because they can be used to express foreign genes in a variety of different hosts.
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FALSE
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One of the major advantages to using plasmids as cloning vectors is that very high copy numbers can be achieved with many types of plasmid vectors.
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TRUE
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A(n)__________ __________ is a piece of DNA with all of the features necessary for chromosomal replication and which can carry large (up to 1000 kb) pieces of foreign DNA into a host organism.
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artificial chromosome
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Cloning a gene involves all of the following except
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expression of the vector and the gene in a cell-free environment.
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The production of large quantities of a particular DNA sequence is known as gene
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amplification
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Which of the following PCR procedures includes all of the others?
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DNA is amplified for one cycle.
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If all of the PCR products of a DNA sequence are 4000 bp, then the DNA sequence that was amplified must have been 8000 bp.
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false
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Which is a true statement regarding the size of PCR products?
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Since the number of DNA products ending exactly between both primers increases with each cycle, when PCR is completed, the majority of products are of similar size.
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Sputum from a patient with a history of tuberculosis due to Mycobacterium tuberculosis bacteria is collected and sent to the microbiology lab for analysis. X-ray analysis and an acid-fast smear made from the sputum indicate that the patient has active tuberculosis. The physician has requested that the sputum be analyzed for pathogen load, but because colonies of Mycobacterium typically take between 3 to 8 weeks to appear on agar, results from traditional culture methods are often delayed. If you were the microbiologist in this case, what would you do?
answer
Using the sputum, apply real-time PCR with primers to Mycobacterium tuberculosis DNA to estimate the pathogen load, then follow up with a traditional culture.
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Which procedure is most useful in quantifying the active transcription of botulism toxin genes in a can of food that is contaminated?
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real time PCR
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The three steps that take place in each cycle during PCR occur in which order?
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DNA denaturation, annealing, and synthesis
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A PCR procedure that allows a determination of the amount of a particular DNA fragment that is present in a sample is called
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real time PCR
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The PCR method was developed by . Mullis.
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Mullis.
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The polymerase chain reaction (PCR) can be used to produce __________ of copies in a few hours.
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billions
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The thermostable enzyme most commonly used in PCR is reverse transcriptase.
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false
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The Southern blotting technique for transferring DNA from an agarose gel to a piece of nitrocellulose membrane is named for E. M. Southern, the person who developed the procedure.
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TRUE
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When separating DNA fragments by gel electrophoresis, what is the purpose of including molecular weight markers?
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Markers are used as a control to determine the relative size of restriction fragments.
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Plasmid DNA having one EcoRI recognition sequence is treated with EcoRI restriction endonuclease. Following gel electrophoresis, how many bands should be visible on the gel?
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one
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If all of the restriction fragments in a DNA digest were of very low molecular weight, then all of the fragments on the electrophoretic gel will be closest to the positive pole and furthest from the negative pole.
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TRUE
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If DNA were a positively charged rather than negatively charged, what change to the gel electrophoresis procedure must be made?
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DNA must be loaded at the positive pole rather than at the negative pole.
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A molecular biologist treats a 600-kb length of linear DNA with HindIII restriction endonuclease. Following gel electrophoresis, the biologist observes that there is only one band on the gel corresponding with the migration distance of the 200-kb molecular weight marker. Assuming that no procedural errors were made, what can be concluded from these results?
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Three HindIII recognition sequences were present in the original DNA.
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Recombinant DNA technology does not rely on which of the following enzymes?
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RNA methylase
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Which of the following is true about restriction endonucleases?
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Some make a blunt cut on the two DNA strands so that there are no single-strand regions and some make staggered cuts on the DNA so that single-strand ends are formed that can be used to insert foreign DNA cut with the same enzyme.
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When a eukaryotic gene is cloned into a bacterium, the advantage of a complementary DNA (cDNA) gene being used instead of fragments of genomic DNA is that
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the introns have been removed from the cDNA gene but not from the genomic fragment.
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Restriction endonucleases in bacteria may have evolved in order to
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protect the bacteria from infection by viruses.
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An enzyme that cleaves internal phosphodiester bonds of a DNA molecule is a (n)
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endonuclease.
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Complementary DNA (cDNA) probes are produced using
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reverse transcriptase.
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A __________ is a DNA molecule used in hybridization reactions to detect the presence of a particular gene in separated DNA fragments.
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probe
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In order to express eukaryotic genes in a bacterium, the __________ must first be removed.
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introns
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Which of the following was first produced commercially using recombinant DNA
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human insulin
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The enzyme reverse transcriptase was discovered by
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Temin and Baltimore.
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Restriction endonucleases were discovered by
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Arber and Smith
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Restriction endonucleases are produced by
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bacteria
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Genetic engineering methods have been used to produce vaccines.
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TRUE
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Movement of charged molecules in an electrical field, which is used to separate nucleic acid fragments for recombinant DNA work, is called
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electrophoresis.
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Which of the following best describes the basis for separation of DNA fragments during agarose gel electrophoresis?
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The smallest fragments will migrate fastest.
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Electroporation is commonly used to introduce recombinant DNA molecules into cells.
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TRUE
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Which is the most frequently chosen prokaryotic host for use in cloning techniques?
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Escherichia coli