Viruses [2] Flashcards
Most known plant viruses have ________-strand RNA genomes, because small genomes ________.
Most known plant viruses have ________-strand RNA genomes, because small genomes ________.
A: positive / interact more readily with host DNA
B: negative / interact more readily with host DNA
C: positive / facilitate cell-to-cell transfer
D: negative / facilitate cell-to-cell transfer
C
What is unusual about phage MS2 infection of Escherichia coli?
A: It enters through a host cell porin.
B: All proteins are synthesized simultaneously during infection so there are no early and late proteins.
C: More than one MS2 phage can be present in an individual E. coli cell.
D: It attaches to the host’s pilus rather than the cell’s surface.
D
Based on its function, which type(s) of viruses likely contain(s) a gene encoding for RNA replicase? A: dsDNA and ssDNA viruses B: positive ssRNA viruses C: positive and negative ssRNA viruses D: ssRNA and ssDNA viruses
C
Polyproteins made from human viruses such as poliovirus must be ________ in order to yield the required functional units of the virus.
A: post-translationally cleaved
B: properly folded into secondary and tertiary structures
C: able to interact with VPg proteins
D: chemically modified with either glycolation or methylation
A
What is the purpose of synthesizing a negative strand RNA in positive stranded ssRNA viruses?
A: enable transcription of genes occurring on both the negative and positive strands of the genome, such as overlapping genes
B: enable rolling circle amplification of the genome, which requires both strands of RNA
C: to serve as the complementary template sequence in genome amplification of the positive strand
D: proofreading of the genome to minimize mutations generated by the polymerase being passed onto virion progeny
C
Among the largest RNA genome viruses are \_\_\_\_\_\_\_\_ which contain a \_\_\_\_\_\_\_\_ genome. A: coronaviruses / dsRNA B: coronaviruses / positive ssRNA C: polioviruses / dsRNA D: polioviruses / positive ssRNA
B
Identifying proteases being essential for replication of a virus would suggest the virus
A: uses at least one set of overlapping genes.
B: lyses its host following genome replication.
C: contains at least one polyprotein.
D: has a single-stranded RNA genome.
C
Because the influenza virus is segmented, when two different strains infect the same cell, a major change in the virus can occur that is called \_\_\_\_\_\_\_\_\_\_. A: viral mutation B: hybridization C: antigenic drift D: antigenic shift
D
The hepadnavirus DNA polymerase acts as which of the following?
A: protein primer for synthesis of a strand of DNA
B: reverse transcriptase
C: DNA polymerase
D: DNA polymerase, reverse transcriptase, and protein primer for DNA synthesis
D
A drug designed to inhibit reverse transcriptase activity would target A: viruses with RNA genomes. B: hepadnaviruses and retroviruses. C: coronaviruses and rhabdoviruses. D: retroviruses.
B
In contrast to positive ssRNA viruses such as coronaviruses and polioviruses, the genome of retroviruses
A: lacks ribonuclease activity.
B: must first integrate into the host’s genome before transcription.
C: is negative ssRNA.
D: lacks genes encoding for tRNA primers.
B
Proteins made by a ribosome reading through a transcript’s stop codon without their own discrete ribosome binding sites
A: suggest a relatively low level of protein product is essential for the virus due to its rare frequency.
B: are thought to be a primitive mechanism to avoid host defenses.
C: appear most abundant in archaeal viruses and relatively uncommon in bacteriophage.
D: create opportunities for viruses to make different capsid proteins.
A
Explain why viroids can only infect and damage plant cells, but not animal cells.
A: Although both types of cells contain RNA, viroids recognize a specific receptor on the surface of plant cells.
B: Plant cells contain a RNA polymerase that can copy RNA can animal cells do not.
C: Animal cells contain RNA polymerase that can copy RNA and plant cells do not.
D: The genome of plant cells is made of RNA while animal cells have a DNA genome.
B
Which statement describes the difference between the normal neuron protein PrPC and the pathogenic version PrPSc?
A: The three-dimensional conformation is identical, but the amino acid sequence is different.
B: PrPC is just a protein and the PrPSc is a protein with nucleic acid inside.
C: The amino acid sequence is identical, but the three-dimensional conformation is different.
D: The PrPC protein contains more beta sheets while the PrPSc protein contains more alpha helices.
C
Retroviruses mutate relatively rapidly. What is one of the reasons?
A: Because retroviruses have multiple enzymes (reverse transcriptase, protease, and integrase), there is more opportunity for error.
B: Reverse transcriptase lacks the proofreading function found in many DNA polymerases, so mutations accumulate more easily.
C: Damage to the reverse transcriptase and other enzymes can lead to increased mutation rates.
D: Retroviruses have a lysogenic life cycle and accumulate mutations while within the host chromosome
B
