Chapter 18-`9 Bio.
Which of the following describes the function of an enzyme known as Dicer?
It trims small double-stranded RNAs into molecules that can block translation.
What is the function of reverse transcriptase in retroviruses?
It uses viral RNA as a template for DNA synthesis.
For a repressible operon to be transcribed, which of the following must occur?
RNA polymerase must bind to the promoter, and the repressor must be inactive.
A researcher lyses a cell that contains nucleic acid molecules and capsomeres of tobacco mosaic virus (TMV). The cell contents are left in a covered test tube overnight. The next day this mixture is sprayed on tobacco plants. Which of the following would be expected to occur?
The plants would develop the typical symptoms of TMV infection.
f a Drosophila female has a homozygous mutation for a maternal effect gene,
all of her offspring will show the mutant phenotype, regardless of their genotype
Altering patterns of gene expression in prokaryotes would most likely serve the organism's survival in which of the following ways?
allowing the organism to adjust to changes in environmental conditions
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?
decrease in glucose and increase in cAMP
Which of the following can be effective in preventing the onset of viral infection in humans?
getting vaccinated
In the figure, at the arrow marked II, what enzyme(s) are being utilized?
host cell DNA polymerase
A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture
increased chromatin condensation
Which of the following experimental procedures is most likely to hasten mRNA degradation in a eukaryotic cell?
removal of the 5' cap
Which viruses have single-stranded RNA that acts as a template for DNA synthesis?
retroviruses
Which of the following statements describes the lysogenic cycle of lambda (ë) phage?
The phage genome replicates along with the host genome.
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.
The transgene integrated into a heterochromatic region of the genome.
The herpes viruses are very important enveloped DNA viruses that cause disease in all vertebrate species and in some invertebrates such as oysters. Some of the human ones are herpes simplex virus (HSV) types I and II, causing facial and genital lesions, and the varicella zoster virus (VSV), causing chicken pox and shingles. Each of these three actively infect nervous tissue. Primary infections are fairly mild, but the virus is not then cleared from the host; rather, viral genomes are maintained in cells in a latent phase. The virus can then reactivate, replicate again, and be infectious to others. In electron micrographs of HSV infection, it can be seen that the intact virus initially reacts with cell surface proteoglycans, then with specific receptors. This is later followed by viral capsids docking with nuclear pores. Afterward, the capsids go from being full to being "empty." Which of the following best fits these observations?
The viral envelope mediates entry into the cell, the capsid entry into the nuclear membrane, and the genome is all that enters the nucleus.
Which of the following is the best predictor of how much damage a virus causes?
ability of the infected cell to undergo normal cell division
In response to chemical signals, prokaryotes can do which of the following?
alter the level of production of various enzymes
What are prions?
misfolded versions of normal brain protein
Transcription of the structural genes in an inducible operon
starts when the pathway's substrate is present.
The product of the bicoid gene in Drosophila provides essential information about
the anterior-posterior axis.