C12 Sample Questions from Brock Flashcards
If a foreign gene is cloned into an expression host, it is important that the host itself
A) not produce the protein being studied.
B) produce the protein in larger amounts than the vector.
C) repress the genetic expression being studied.
D) produce signal proteins to tag the host protein.
A) not produce the protein being studied.
To avoid interference or confusion between the host’s native protein and the cloned protein. This ensures accurate analysis of the cloned protein’s function and expression.
Cells that have “insertional inactivation” of the lacZ gene are
A) blue.
B) white.
C) yellow.
D) fluorescent green.
B) white.
Insertional inactivation disrupts the lacZ gene, preventing β-galactosidase production, which normally turns cells blue on X-gal medium, so affected cells remain white.
Cosmids are a type of
A) bacterial artificial chromosomes (BACs).
B) cloning vector.
C) heat stable polymerase.
D) RNA/DNA hybrid.
B) cloning vector.
Cosmids are specialized vectors that combine features of plasmids and phages, designed for cloning larger DNA fragments.
Expression vectors are designed to ensure that ________ can be efficiently __________.
A) mRNA / transcribed
B) DNA / transcribed
C) mRNA / translated
D) DNA / translated
C) mRNA / translated
Expression vectors aim to facilitate the efficient translation of mRNA into protein, ensuring high levels of the protein of interest are produced.
A(n) ______ gene is a gene that encodes a protein that is easy to detect and assay.
A) encoder
B) translational
C) reporter
D) recorder
C) reporter
Reporter genes (e.g., GFP, lacZ) encode easily detectable proteins, allowing researchers to monitor gene expression or verify cloning success.
One of the more formidable obstacles to mammalian gene cloning is the presence of
A) introns.
B) exons.
C) repressors.
D) integrators.
A) introns.
Introns are non-coding DNA sequences found in eukaryotic genes, which can complicate the cloning process due to the need for splicing to produce a functional protein.
What is the most important advantage of Pfu polymerase over Taq polymerase?
A) Unlike Taq polymerase, Pfu polymerase functions well at relatively high temperatures.
B) It is from a bacterium, not an archaean, so it is more effective for replicating eukaryotic DNA.
C) Pfu polymerase removes the need for primers during PCR.
D) Unlike Taq polymerase, Pfu polymerase has proofreading activity.
D) Unlike Taq polymerase, Pfu polymerase has proofreading activity.
Pfu polymerase’s proofreading capability reduces error rates during PCR, yielding more accurate amplicons compared to Taq polymerase.
What is the difference between PCR and RT-PCR?
A) Only PCR makes many copies of DNA rapidly.
B) RT-PCR uses an RNA template whereas PCR uses a DNA template.
C) Only PCR produces cDNA.
D) PCR uses a single stranded template whereas RT-PCR uses a double-stranded template.
B) RT-PCR uses an RNA template whereas PCR uses a DNA template.
RT-PCR (Reverse Transcription PCR) first converts RNA into cDNA, which is then amplified, distinguishing it from standard PCR that amplifies DNA templates directly.
The genes encoding green fluorescent protein (GFP) and β-galactosidase are typically used in cloning as
A) transcription regulators.
B) global control genes.
C) promoter sequences.
D) reporter genes.
D) reporter genes.
Both GFP and β-galactosidase serve as markers to indicate successful cloning, expression, or localization of a gene of interest.
To verify a gene was cloned into a vector successfully, sequencing the vector as well as ______ are commonly performed.
A) agarose gel electrophoresis
B) fluorescence in situ hybridization
C) protein purification
D) northern blots
A) agarose gel electrophoresis
While sequencing confirms the gene’s presence and accuracy, agarose gel electrophoresis provides a quicker, preliminary check for the insert’s size and presence.
Which objective would be best to use a Southern blot rather than a Northern blot?
A) Determine if a gene is present in a genome.
B) Discover gene function.
C) Identify regulatory gene-protein interactions.
D) Quantify expression profiles of a gene.
A) Determine if a gene is present in a genome.
Southern blots detect DNA sequences, making them suitable for genomic analysis, whereas Northern blots are used for RNA (gene expression) analysis.
A polymerase chain reaction (PCR) copies an individual gene segment in vitro with a(n) _____ primer(s).
A) individual RNA
B) individual DNA
C) pair of RNA
D) pair of DNA
D) pair of DNA
PCR requires a pair of DNA primers, one for each strand of the DNA, to initiate and direct the amplification process.
Which of the following sequences is a palindrome, characteristic of many recognition sequences for restriction endonucleases?
A) TTGCCGA / AACGGCT
B) GGGGGGG / CCCCCCCC
C) GTAATG / CATTAC
D) GAATTC / CTTAAG
D) GAATTC / CTTAAG
Palindromic sequences read the same backward as forward, a common feature of restriction enzyme recognition sites, exemplified by the EcoRI site (GAATTC).
At which time period(s) during PCR thermocycling is/are hottest in temperature?
A) during DNA denaturation
B) during primer annealing
C) during primer extension/elongation
D) Both the first and last cycles are hotter in temperature than all other cycles.
A) during DNA denaturation
Denaturation, the first step of a PCR cycle, requires the highest temperature to melt the DNA double helix into single strands.
To estimate the total concentration of a beneficial bacterial species in yogurt, _________ would provide the quickest results.
A) fluorescence in situ hybridization
B) qPCR
C) RT-PCR
D) a Southern blot
B) qPCR
Quantitative Polymerase Chain Reaction (qPCR) is designed for rapid, precise quantification of specific DNA sequences, making it ideal for estimating microbial concentrations.
Which of the following is NOT a common step in molecular cloning using plasmids?
A) Fragment DNA into small segments.
B) Hybridize DNA sequences with slightly mismatched oligonucleotides.
C) Ligate DNA into vectors.
D) Insert the vectors into a host.
B) Hybridize DNA sequences with slightly mismatched oligonucleotides.
While hybridization is a technique used in molecular biology, the description given doesn’t accurately represent a standard step in plasmid-based cloning, which typically involves cutting, ligating, transforming, and selecting.
What molecular mechanism/feature does site-directed mutagenesis exploit to introduce a mutation at a specific site?
A) flanking complementary bound nucleotides permit non-complementary base pairing
B) methylated nucleotides disrupt DNA polymeraseʹs proofreading
C) nucleotide substitution when one is depleted
D) transposase-induced base pair changes
A) flanking complementary bound nucleotides permit non-complementary base pairing
Site-directed mutagenesis often uses primers with deliberate mismatches that are complementary to the target site, allowing for precise introduction of mutations during PCR.
Inserting a kanamycin resistance cassette into a catabolic operon to confirm the gene is essential in degradation of a particular compound would involve all of the following EXCEPT
A) a reporter gene.
B) ligation.
C) recombination.
D) transformation.
A) a reporter gene.
This process involves disrupting the gene with an antibiotic resistance cassette to assess the gene’s necessity, not typically using a reporter gene, which would be used to monitor expression levels.
Which statement is TRUE?
A) YACs are more likely than BACs to undergo recombination and rearrangement.
B) BACs are more likely than YACs to undergo recombination and rearrangement.
C) YACs and BACs undergo recombination and rearrangement at about the same rate.
D) It is impossible to state with any certainty whether YACs or BACs are more likely to undergo recombination and rearrangement, because environmental factors play a major role in the probability of one or the other occurring.
A) YACs are more likely than BACs to undergo recombination and rearrangement.
Yeast Artificial Chromosomes (YACs) are indeed more prone to recombination and rearrangements compared to Bacterial Artificial Chromosomes (BACs), due to the nature of yeast versus bacterial hosts.
Which of those listed below is LEAST similar in what is being studied and concluded?
A) fluorescence in situ hybridization
B) GFP fusion protein
C) Northern blot
D) RT-PCR
C) Northern blot
The other options (fluorescence in situ hybridization, GFP fusion protein, RT-PCR) are primarily used for localization, protein expression, or mRNA quantification, whereas Northern blots specifically analyze RNA expression levels, making it the least similar in application among the listed methods.
The principle behind nucleic acid probe design is that the probe itself must contain
A) a key complementary part of the target gene sequence of interest.
B) all of the nucleotide sequence of the gene of interest to conclusively identify the gene.
C) an antibody to specifically bind to the gene of interest.
D) at least three separate complementary regions of the gene of interest.
A) a key complementary part of the target gene sequence of interest.
Probes are designed to specifically bind to their target sequence through complementary base pairing, enabling detection or localization of the target within a sample.
Which of those below is NOT an important consideration when designing a fusion protein construct?
A) Avoid hybridization of the fusion gene in the artificial construct.
B) Reading frame is the same for both the fusion gene and reporter gene.
C) Transcriptional start and stop signals are shared.
D) Translational start and stop signals are shared.
A) Avoid hybridization of the fusion gene in the artificial construct.
While avoiding unwanted interactions is generally good practice, the specific concern about hybridization of the fusion gene itself is less critical than ensuring the reading frame, transcriptional, and translational signals are correctly aligned.
One challenge in cloning human somatotropin is that
A) it consists of multiple polypeptides, making synthesis complex.
B) its gene cannot be cloned as cDNA.
C) it can only be expressed by eukaryotic cells.
D) it is susceptible to digestion by bacterial proteases because it is a small protein hormone.
D) it is susceptible to digestion by bacterial proteases because it is a small protein hormone.
Human somatotropin (growth hormone) being a small protein makes it more vulnerable to degradation by host cell proteases, complicating its production in bacterial systems.
After digesting a DNA sequence, a restriction endonuclease can generate
A) blunt ends.
B) overhangs.
C) sticky ends.
D) blunt ends, overhangs, or sticky ends.
D) blunt ends, overhangs, or sticky ends.
Different restriction enzymes can produce various types of ends, including blunt (straight cut), overhangs (sticky ends with a short single-stranded segment), or a combination thereof, depending on the enzyme used.
What is the first step in constructing a metagenomic library from RNA?
A) The RNA must be converted to cDNA.
B) The RNA must be amplified through PCR, producing many RNA copies.
C) The RNA must be screened to identify the genes of interest.
D) The RNA must be inserted into plasmid vectors.
A) The RNA must be converted to cDNA.
Since metagenomic libraries are typically constructed in DNA form, the initial step when starting with RNA involves reverse transcription to convert the RNA into complementary DNA (cDNA).
