RNAi methodology uses double-stranded pieces of RNA to trigger a breakdown or blocking of mRNA. For which of the following might it more possibly be useful?
A) to decrease the production from a harmful gain-of-function mutated gene
B) to raise the rate of production of a needed digestive enzyme
C) to raise the concentration of a desired protein
D) to destroy an unwanted allele in a homozygous individual
E) to form a knockout organism that will not pass the deleted sequence to its progeny
Viral envelopes can best be analyzed with which of the following techniques?
A) transmission electron microscopy
B) staining and visualization with the light microscope
C) immunofluorescent tagging of capsid proteins
D) antibodies against specific proteins not found in the host membranes
E) use of plaque assays for quantitative measurement of viral titer
A researcher introduces double-stranded RNA into a culture of mammalian cells, and can identify its location or that of its smaller subsections experimentally, using a fluorescent probe. Within the first quarter hour, the researcher sees that the intact RNA is found in the cells. After 3 hours, she is not surprised to find that
A) the double-stranded RNA binds to mRNAs to prevent translation.
B) the double-stranded RNA replicates itself.
C) the RNA is degraded by 5' and 3' exonucleases.
D) Dicer enzyme has reduced it to smaller double-stranded pieces.
E) the double-stranded RNA binds to tRNAs to prevent translation.
DNA fragments from a gel are transferred to a nitrocellulose paper during the procedure called Southern blotting. What is the purpose of transferring the DNA from a gel to a nitrocellulose paper?
A) to attach the DNA fragments to a permanent substrate
B) to prepare the DNA for digestion with restriction enzymes
C) to separate the two complementary DNA strands
D) to separate out the PCRs
E) to transfer only the DNA that is of interest
How does a bacterial cell protect its own DNA from restriction enzymes? A) by adding histones to protect the double-stranded DNA
B) by forming "sticky ends" of bacterial DNA to prevent the enzyme from attaching
C) by adding methyl groups to adenines and cytosines
D) by reinforcing the bacterial DNA structure with covalent phosphodiester bonds
E) by using DNA ligase to seal the bacterial DNA into a closed circle
aA) to attach the DNA fragments to a permanent substrate
bD) Dicer enzyme has reduced it to smaller double-stranded pieces
cC) by adding methyl groups to adenines and cytosines
dD) antibodies against specific proteins not found in the host membranes
eA) to decrease the production from a harmful gain-of-function mutated gene
5 Multiple Choice Questions
B) increased chromatin condensation
E) bind to the repressor protein and activate it
B) Transferred genes may not have appropriately controlled activity
C) decrease in glucose and increase in cAMP
B) binding to intracellular receptors and promoting transcription of specific genes
5 True/False Questions
Why might a laboratory be using dideoxy nucleotides?
A) to visualize DNA expression
B) to separate DNA fragments
C) to clone the breakpoints of cut DNA
D) to sequence a DNA fragment
E) to produce cDNA from mRNA → C) it uses viral RNA as a template for DNA synthesis
A mutation that inactivates the regulatory gene of a repressible operon in an E. coli cell would result in
A) irreversible binding of the repressor to the operator.
B) continuous transcription of the structural gene controlled by that regulator.
C) inactivation of RNA polymerase by alteration of its active site.
D) complete inhibition of transcription of the structural gene controlled by that regulator.
E) continuous translation of the mRNA because of alteration of its structure. → E) bind to the repressor protein and activate it
What would occur if the repressor of an inducible operon were mutated so it could not bind the operator?
A) buildup of a substrate for the pathway controlled by the operon
B) reduced transcription of the operon's genes
C) irreversible binding of the repressor to the promoter
D) continuous transcription of the operon's genes
E) overproduction of catabolite activator protein (CAP) → D) continuous transcription of the operon's genes
One hereditary disease in humans, called xeroderma pigmentosum (XP), makes homozygous individuals exceptionally susceptible to UV-induced mutation damage in the cells of exposed tissue, especially skin. Without extraordinary avoidance of sunlight exposure, patients soon succumb to numerous skin cancers. Which of the following best describes this phenomenon? A) inherited predisposition to mutation
B) susceptibility to chemical carcinogens
C) inherited inability to repair UV-induced mutation
D) embryonic or fetal cancer
E) inherited cancer taking a few years to be expressed → E) abnormalities of mouse embryos
What are prions?
A) mobile segments of DNA
B) viruses that invade bacteria
C) tiny molecules of RNA that infect plants
D) misfolded versions of normal brain protein
E) viral DNA that has had to attach itself to the host genome → C) a somatic plant cell can often give rise to a complete plant