Which of the following represents a difference between viruses and viroids?
A) Viruses have capsids composed of protein, whereas viroids have no capsids.
B) Viruses cannot pass through plasmodesmata, whereas viroids can.
C) Viruses contain introns, whereas viroids have only exons.
D) Viruses infect many types of cells, whereas viroids infect only prokaryotic cells.
E) Viruses always have genomes composed of DNA, whereas viroids always have genomes composed of RNA.
Which of the following tools of recombinant DNA technology is incorrectly paired with its use?
A) restriction enzyme--analysis of RFLPs
B) reverse transcriptase--production of cDNA from mRNA
C) electrophoresis--separation of DNA fragments
D) DNA ligase--cutting DNA, creating sticky ends of restriction fragments
E) DNA polymerase--polymerase chain reaction to amplify sections of DNA
Which viruses have single-stranded RNA that acts as a template for DNA synthesis?
A) lytic phages
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.
In the figure, at the arrow marked II, what enzyme(s) are being utilized? A) host cell RNA polymerase
B) host cell DNA polymerase
C) reverse transcriptase
D) viral DNA polymerase
E) host cell DNA and RNA polymerases
aD) DNA ligase-- cutting DNA, creating sticky ends of restriction fragments
bC) Viral genomes are usually similar to the genome of the host cell
cB) host cell DNA polymerase
eA) viruses have capsids composed of protein, whereas viroids have no capsids
5 Multiple Choice Questions
E) abnormalities of mouse embryos
B) continuous transcripton of the structural gene controlled by that regulator
C) mutation of existing viruses, the spread of existing viruses to new host species, and the spread of existing viruses more widely within their host species
C) by adding methyl groups to adenines and cytosines
5 True/False Questions
In 1997, Dolly the sheep was cloned. Which of the following processes was used?
A) fusion of an adult cell's nucleus with an enucleated sheep egg, followed by incubation in a
B) replication and dedifferentiation of adult stem cells from sheep bone marrow
C) separation of an early stage sheep blastula into separate cells, one of which was incubated in a surrogate ewe
D) isolation of stem cells from a lamb embryo and production of a zygote equivalent
E) use of mitochondrial DNA from adult female cells of another ewe → A) fusion of an adult cell's nucleus with an enucleated sheep egg, followed by incubation in a surrogate
Expression of a cloned eukaryotic gene in a bacterial cell involves many challenges. The use of mRNA and reverse transcriptase is part of a strategy to solve the problem of
A) post-translational processing.
B) restriction fragment ligation.
C) nucleic acid hybridization.
D) post-transcriptional processing.
E) electroporation. → D) post-transcriptional processing
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 → C) inherited inability to repair UV-induced mutation
A geneticist introduces a transgene into yeast cells and isolates five independent cell lines in which the transgene has integrated into the yeast genome. In four of the lines, the transgene is expressed strongly, but in the fifth there is no expression at all. Of the lines that express the transgene, one is transcribed but not translated. Which of the following is a likely explanation?
A) high histone acetylation
B) no compatible ribosome
C) missing transcription factor
D) no AUG in any frame
E) no promoter → D) post-transcriptional processing
The host range of a virus is determined by
A) the proteins in the host's cytoplasm.
B) the enzymes carried by the virus. C) whether its nucleic acid is DNA or RNA.
D) the proteins on its surface and that of the host.
E) the enzymes produced by the virus before it infects the cell. → B) binding to intracellular receptors and promoting transcription of specific genes