Rule of six (viruses)

The rule of six is a feature of some paramyxovirus genomes. These RNA viruses 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]

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

For the Coronavirus restriction, see The Health Protection (Coronavirus, Restrictions) (No. 2) (England) Regulations 2020 § 'Rule of six'.