Review Question - QID 106972

Although it is surrounded by the nucleocapsid of virus Y, the virus genome of X has not been altered, and therefore, the next generation of virions produced will contain the genome and nucleocapsid encoded by genome X. This is referred to as phenotypic mixing.

Phenotypic mixing occurs when two or more viruses infect a cell. When the viruses begin to replicate, the genomes of the viruses may be coated by the nucleocapsids of either virus. If the situation occurs where one genome is coated by the nucleocapsid of another virus, a pseudovirion is formed. It is important to note that the genome is not altered although it is coated by another nucleocapsid of a different virus. When this virus infects another cell, the progeny will NOT produce the same nucleocapsid as its parent, but the nucleocapsid that is encoded by its genome. Hence, it will produce a virion like the original virus.

Griffith et al. reviews an example of when two different genomes from two infecting agents are within a cell at one time; it is possible that the gene products from one may be able to compensate for the dysfunctional or absent genes of the other. This supplying of function by one infecting agent to the other is called complementation. Progeny of the dysfunctional agent may be produced, but the progeny will will require complementation again to replicate when they infect another cell.

Incorrect Answers:
Answers 1, 3-5: A virion of genome X and nucleocapsid X will be produced. These choices cannot be produced.