A scientist discovers a new virus associated with a cancer. She is able to culture it in the laboratory and begins to analyze it. What features will help her determine the virus' classification? How does this help her understand the virus' mechanism for causing cancer?

Question

What will be an ideal response?

Answer 1

Characterization of the nucleic acid present in the virion is a first step in determining the classification of the virus. If it is a large DNA virus with envelope, it may be one of the Herpesviridae. DNA viruses with smaller genome sizes known to cause cancer are the Papillomaviruses and Polyomaviruses. The Hepadnavirdae have a circular DNA molecule which is partially double strand and partially single strand. Very small DNA viruses which occasionally cause cancer are the Adenoviridae. The presence or absence of an envelope is also useful in eliminating possibilities. The presence of a segmented genome comprised of + single-strand RNA and the enzyme reverse transcriptase is consistent with the virus being a member of the Retroviridae.
DNA sequence determination is useful for verifying the classification to a family or genus.
Establishing the classification of the virus can provide clues as to the possible mechanism of causing cancer, as different virus families are involved in different processes. For example, retroviruses integrate into the host DNA and may thereby disrupt the function of a tumor repressor.