RNA virus

A virus in which the genetic material is RNA.

The RNA may be either double- or single-stranded.</P> 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.