Topic 19: Viruses & Prions Flashcards
Which of the following molecules are NOT components of the viral envelope?
a. ) Viral glycoproteins
b. ) Viral DNA
c. ) Phospholipids from host cell membrane
d. ) Membrane proteins from host cell
b.) Viral DNA
Which of the following is a property of life shared by prokaryotic cells and eukaryotic cells, but not viruses?
a. ) Nucleic acids used to store hereditary information
b. ) The capacity to evolve
c. ) The ability to process energy through metabolic reactions
d. ) Order and complexity in arrangement of biological molecules
c.) The ability to process energy through metabolic reactions
A microbiologist analyzes chemicals obtained from an enveloped RNA virus that infects monkeys. He finds that the viral envelope contains a protein characteristic of monkey cells. Which of the following is the most likely explanation?
a. ) The viral envelope forms as the virus leaves the host cell.
b. ) The virus forced the monkey cell to make proteins for its envelope.
c. ) The virus fools its host by mimicking its proteins.
d. ) Its presence is a result of the monkey’s immunological response.
a. ) The viral envelope forms as the virus leaves the host cell.
* An enveloped virus is wrapped in the host plasma membrane or nuclear membrane (which contains host proteins).
Viruses are…
a. ) All of these answers are correct.
b. ) Much smaller than eukaryotic cells.
c. ) Much smaller than prokaryotic cells.
d. ) Simpler in structure than cells.
a.) All of these answers are correct.
When comparing DNA and RNA viruses, which mutate more quickly, and why?
a. ) RNA viruses because RNA is single-stranded and thus more prone to mutations
b. ) They all mutate at the same rate.
c. ) DNA viruses because they usually have larger genomes and thus more loci for mutations to occur
d. ) RNA viruses because no proofreading is done on RNA molecules
d.) RNA viruses because no proofreading is done on RNA molecules
Which of the following is/are effective means of avoiding infection with a prion disease?
a. ) None of these measures is effective.
b. ) Take certain antibiotics as a preventative measure.
c. ) Make sure any meat you eat is completely cooked.
d. ) Get vaccinated against the most common form of human prion disease.
a. ) None of these measures is effective.
* Cooking to normal temperatures will not protect against infection with a prion disease. There are no drugs (e.g., antibiotics) or vaccines available for protection against prion disease. Fortunately prion disease is very rare in humans.
When a virus infects an E. coli cell, what part of the virus enters the bacterial cytoplasm?
a. ) The entire virus
b. ) The protein capsid and enclosed nucleic acid
c. ) The tail fibers
d. ) Only the nucleic acid
d.) Only the nucleic acid
What is the function of reverse transcriptase in retroviruses?
a. ) It uses viral RNA as a template for making complementary RNA strands.
b. ) It converts host cell RNA into viral DNA.
c. ) It translates viral RNA into proteins.
d. ) It uses viral RNA as a template for DNA synthesis.
d. ) It uses viral RNA as a template for DNA synthesis.
* “Reverse transcriptase” gets its name from the fact that it does things in the reverse way as usual. Usually, a DNA molecule is used as a template to make an RNA molecule. In contrast, reverse transcriptase uses an RNA molecule as a template to make a DNA molecule. Reverse transcriptase is critical in replication of retroviruses, which have genomes made of RNA. During the replication of retroviruses, reverse transcriptase uses the RNA genome of the virus as a template to make a DNA molecule.
Covid-19…
a. ) Has a genome composed of RNA and so mutates relatively quickly.
b. ) Has a genome composed of DNA and so mutates relatively quickly.
c. ) Has a genome composed of DNA and so mutates relatively slowly.
d. ) Has a genome composed of RNA and so mutates relatively slowly.
a.) Has a genome composed of RNA and so mutates relatively quickly.
A phage that replicates only by a lytic cycle is known as a…
a. ) Temperate phage
b. ) Virulent phage
c. ) Lyson
d. ) Prion
b.) Virulent phage
An infectious particle is found that contains only protein. This particle is best characterized as a…
a. ) Retrovirus
b. ) Phage
c. ) Prion
d. ) Bacterium
c.) Prion
“Restriction enzymes” can…
a. ) Protect bacteria against infection by prions
b. ) Protect bacteria against infection by bacteriophages
c. ) Protect bacteria against infection by retroviruses
d. ) All of these answers are correct.
b.) Protect bacteria against infection by bacteriophages
*“Restriction enzymes” are enzymes that cut DNA molecules at specific nucleotide sequences. Some bacteria produce restriction enzymes that help protect them against infection by bacteriophages by cutting up the viral DNA of any bacteriophage that tries to infect them. The DNA of the bacterium is protected by being methylated by the bacteria.
Retroviruses infect animal cells rather than bacteria.
Prions infect animal cells rather than bacteria. In addition, prions are made solely of protein and so would not be affected by a restriction enzyme.
Which of the following does NOT constitute any known type of virus particle?
a. ) Protein plus lipid envelope
b. ) Single-stranded RNA plus protein plus lipid envelope
c. ) Single-stranded DNA plus protein
d. ) Double-stranded RNA plus protein
a.) Protein plus lipid envelope
In considering the differences between lytic and lysogenic cycles of bacteriophages, which of the following is uniquely characteristic of the lytic cycle?
a. ) Phage self-assembly
b. ) Prophage
c. ) Bacterial division
d. ) Replication of phage DNA
a.) Phage self-assembly
An enzyme that recognizes and cuts DNA molecules that are foreign to a bacterium, such as phage genomes, is known as a…
a. ) Cutter enzyme
b. ) Killer enzyme
c. ) Restriction enzyme
d. ) Capsomere
c.) Restriction enzyme
