Definition of RNA virus RNA virus: A virus in which the genetic
material is RNA. The RNA may be either double- or single-
stranded. There are 6 classes of viruses. The DNA viruses
constitute classes I and II. The RNA viruses make up the
remaining classes. Class III viruses have a double-stranded RNA
genome. Class IV viruses have a positive single-stranded RNA
genome, the genome itself acting as mRNA (messenger RNA. Class V
viruses have a negative single-stranded RNA genome used as a
template for mRNA synthesis. Class VI viruses have a positive
single- stranded RNA genome but with a DNA intermediate not only
in replication but also in mRNA synthesis. Last Editorial
Review: 6/14/2012 Back to MedTerms online medical dictionary A-Z
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