5 Written questions
5 Matching questions
- 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
- Some viruses can be crystallized and their structures analyzed. One such virus isDesmodium, or yellow mottle virus, which infects beans. This is a member of the tymovirus group and has a single-stranded RNA genome of ~6,300 nucleotides. Its virion is 25—30 nm in diameter, and is made up of 180 copies of a single capsid protein that self-associate to form each capsomere, which has icosahedral symmetry with 20 facets.
If this virus has capsomeres with 20 facets, how many proteins form each one?
- 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
- Poliovirus is a positive-sense RNA virus of the picornavirus group. At its 5' end, the RNA genome has a viral protein (VPg) instead of a 5' cap. This is followed by a nontranslated leader sequence, and then a single long protein coding region (~7,000 nucleotides), followed by a poly-A tail. Observations were made that used radioactive amino acid analogues. Short period use of the radioactive amino acids result in labeling of only very long proteins, while longer periods of labeling result in several different short polypeptides.
What conclusion is most consistent with the results of the radioactive labeling experiment? ]
A) The large radioactive polypeptides are coded by the host, whereas the short ones are
coded for by the virus.
B) The host cell cannot translate viral protein with the amino acid analogues.
C) The RNA is only translated into a single long polypeptide, which is then cleaved into shorter ones.
D) Host cell ribosomes only translate the viral code into short polypeptides.
E) The RNA is translated into short polypeptides, which are subsequently assembled into
- What is the function of reverse transcriptase in retroviruses?
A) It translates viral RNA into proteins.
B) It uses viral RNA as a template for making complementary RNA strands.
C) It uses viral RNA as a template for DNA synthesis.
D) It hydrolyzes the host cell's DNA. E) It converts host cell RNA into viral DNA.
- a D) antibodies against specific proteins not found in the host membranes
- b A) to attach the DNA fragments to a permanent substrate
- c C) it uses viral RNA as a template for DNA synthesis
- d C) The RNA is only translated into a single long polypeptide, which is then cleaved into shorter ones
- e B) ~6
5 Multiple choice questions
- D) Dicer enzyme has reduced it to smaller double-stranded pieces
- D) the proteins on its surface and that of the host
- A) viruses have capsids composed of protein, whereas viroids have no capsids
- D) continuous transcription of the operon's genes
- B) methylation of the DNA is maintained because methylation enzymes act at DNA sites where one strand is already methylated and thus correctly methylates daughter strands after replication
5 True/False questions
In positive control of several sugar-metabolism-related operons, the catabolite activator protein (CAP) binds to DNA to stimulate transcription. What causes an increase in CAP?
A) increase in glucose and increase in cAMP
B) increase in glucose and decrease in cAMP
C) decrease in glucose and increase in cAMP
D) decrease in glucose and increase in repressor
E) decrease in glucose and decrease in repressor → C) decrease in glucose and increase in cAMP
A) are frequently overexpressed in cancerous cells.
B) do all of the above.
C) can encode proteins that promote DNA repair or cell-cell adhesion.
D) often encode proteins that stimulate the cell cycle.
E) are cancer-causing genes introduced into cells by viruses. → C) can encode proteins that promote DNA repair or cell-cell adhesion
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. → B) continuous transcripton of the structural gene controlled by that regulator
A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture.In one set of experiments using this procedure in Drosophila, she was readily successful in increasing phosphorylation of amino acids adjacent to methylated amino acids in histone tails. Which of the following results would she most likely see?
A) inactivation of the selected genes B) decreased chromatin condensation
C) abnormalities of mouse embryos D) decreased binding of transcription factors
E) increased chromatin condensation → D) A retrovirus is used to introduce four specific regulatory genes
Most molecular biologists think that viruses originated from fragments of cellular nucleic acid. Which of the following observations supports this theory?
A) Viruses are enclosed in protein capsids rather than plasma membranes.
B) Viruses contain either DNA or RNA.
C) Viral genomes are usually similar to the genome of the host cell.
D) Viruses can reproduce only inside host cells.
E) Viruses can infect both prokaryotic and eukaryotic cells. → all