Which property of an enveloped virus most limits its survival outside the host?
Answer: C
The envelope is host-derived lipid, and once it is damaged the glycoproteins it carries can no longer bring about attachment and entry. That fragility shapes how such viruses spread and how easily they are disinfected.
Please log in or register to report this question.
Cytopathic effect refers to
Answer: D
Correct answer: visible damage to cells caused by viral infection
The cytopathic effect is what the infection does to the cell as seen down the microscope - rounding, detachment, syncytium formation, inclusion bodies, lysis. It is the basis of detecting a virus in cell culture, and the pattern is often characteristic enough to suggest which virus is present before any other test is done.
Please log in or register to report this question.
A plaque appears in a monolayer because
Answer: A
Correct answer: infected cells have died, leaving a clear area
A plaque is a hole in the monolayer. One infectious particle infects one cell, the progeny spread to the neighbours under a semi-solid overlay that prevents diffusion, and the successive rounds of killing leave a clear patch against the stained sheet of surviving cells. Because each plaque traces back to a single particle, counting plaques counts infectious units.
Please log in or register to report this question.
Which statement correctly contrasts a virus with a bacterium?
Answer: B
Carrying one type of nucleic acid rather than both is one of the clearest distinctions, alongside the absence of ribosomes and of energy generation. Bacteria are cells and divide in two; viruses are assembled from separately made parts.
Please log in or register to report this question.
Which is NOT a property of viruses?
Answer: C
Correct answer: Growth in size before dividing
Viruses do not grow and divide. They are assembled from separately synthesised components, so a cell yields hundreds of complete particles at once rather than a parent particle enlarging and splitting. The other three are all defining properties: a protein coat, a nucleic acid genome, and replication only inside a host cell.
Please log in or register to report this question.
The protein coat of a virus is described as virus-coded, meaning it is
Answer: D
The instructions come from the virus but the ribosomes doing the work belong to the cell, which is the arrangement for every viral protein. The envelope is the opposite case, being host lipid carrying virus-coded glycoproteins.
Please log in or register to report this question.
Which sequence gives the correct order of the multiplication cycle?
Answer: A
Correct answer: Attachment, penetration, uncoating, synthesis, maturation, egress
The order is fixed by what each step requires of the one before. The particle must attach to its receptor before it can enter, must enter before the genome can be released, must release the genome before anything can be synthesised, and must synthesise the components before they can be assembled and released. Between uncoating and maturation lies the eclipse phase, when no infectious virus can be recovered from the cell at all.
Please log in or register to report this question.
The genome of a virus is enclosed by a coat that is
Answer: B
Correct answer: virus-coded protein
The capsid is built from protein subunits encoded by the viral genome and made by the host’s ribosomes. That distinguishes it sharply from the envelope of an enveloped virus, which is host-derived lipid membrane carrying virus-coded glycoproteins - the lipid is the cell’s, the protein in it is the virus’s.
Please log in or register to report this question.
Which structure is found in some viruses but not all?
Answer: C
Correct answer: The envelope
Every virus has a genome and a capsid, and the two together are the nucleocapsid, so those three are universal. The envelope is not: it is acquired by budding through a host membrane and is present in some families and absent in others. The difference is practical as well as structural, since an enveloped virus is readily inactivated by detergents, solvents and drying, while a naked one is much more robust.
Please log in or register to report this question.
A virus that has lost its envelope is best described as
Answer: D
The envelope carries the glycoproteins that bring about attachment and entry, so a stripped particle cannot begin a new cycle even with its genome intact. This is why lipid solvents inactivate enveloped viruses so readily.
Please log in or register to report this question.
