During budding, the viral glycoproteins are
Answer: C
Virus-encoded glycoproteins are processed through the cell's membrane pathway and placed in the patch of membrane that the nucleocapsid then buds through, so the finished envelope carries viral spikes in host lipid. That mixed origin is exactly what the envelope is.
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The visible degenerative changes produced in cultured cells by a virus are called
Answer: D
Rounding, detachment, fusion and lysis of cells in a monolayer are collectively the cytopathic effect, and the pattern is characteristic enough to suggest which virus is present. Its appearance is the usual first indication that an inoculated culture is infected.
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Negri bodies are inclusion bodies characteristically found in
Answer: A
Negri bodies are eosinophilic cytoplasmic inclusions seen in neurons, classically in the hippocampus and cerebellum, and their presence has long been used to confirm rabies at post-mortem. Inclusion bodies in general are sites of viral assembly or accumulated viral material.
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Multinucleate giant cells formed by fusion of infected cells are called
Answer: B
Some enveloped viruses place fusion glycoproteins in the cell surface, so infected cells merge with their neighbours into a syncytium. Measles and respiratory syncytial virus are the familiar examples, and the effect lets the virus spread without entering the extracellular space.
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A lytic virus infection ends with
Answer: C
Cells infected by a lytic virus cease their metabolic activity and lose structural integrity, releasing progeny as they break down. That is the opposite of a latent or a persistent non-cytolytic infection, in which the cell survives and may keep producing virus.
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A virus that remains in the host without producing progeny, able to reactivate later, is said to be
Answer: D
In latency the genome persists in the cell with little or no gene expression and no progeny, and some later stimulus restarts the productive cycle. Herpes simplex virus in sensory ganglia is the standard example, and it is why a first infection can recur for a lifetime.
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Herpes simplex virus characteristically establishes latency in
Answer: A
After the initial mucosal infection the virus travels along sensory axons to the ganglion and persists in the neurons there. Because neurons are long-lived and poorly visible to the immune system, the reservoir is permanent and reactivation delivers virus back to the same skin territory.
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Which one of the following viruses is associated with cervical carcinoma?
Answer: B
Persistent infection with high-risk papillomavirus types is the necessary cause of almost all cervical cancer, acting through viral proteins that disable the cell's tumour suppressors. The other three viruses cause acute illness and are not oncogenic.
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Epstein-Barr virus is a member of the
Answer: C
Epstein-Barr virus is a human herpesvirus, so it carries double-stranded DNA and establishes lifelong latency, in this case chiefly in B lymphocytes. That combination of persistence and lymphocyte tropism underlies both infectious mononucleosis and its associated lymphomas.
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A virus that transforms a cell typically produces a cell that
Answer: D
Transformation means the infected cell acquires unregulated growth, continuing to divide where a normal cell would stop. Because the cell survives rather than lysing, the viral genome is retained and passed to daughter cells, which is how a tumour clone arises.
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