Rule of six (viruses)

Electron micrograph of the ribonucleoprotein of mumps virus, which has a herring-bone like structure

The rule of six is feature of some paramyxovirus genomes. These are RNA viruses which have genes made from RNA and not DNA, and their whole genome – that is the number of nucleotides – is always a multiple of six. This is because during their replication, these viruses are dependent on nucleoprotein molecules that each bind to six nucleotides.^[1]

1. Easton, AJ and Ling R (2010). Mahy BWJ and Van Regenmortel MHV, ed. Desk Encylopedia of General Virology. Academic Press. p. 496. ISBN 9780123751461..