A Nucleocapsid is the genome (DNA or RNA) of a virus and the protein coat surrounding it (the capsid). There may be proteins complexed with the genome (nucleoproteins) that are also considered part of the nucleocapsid. In simple viruses, the nucleocapsid may constitute the whole virus - poliovirus is an example. Alternatively, most other viruses are more complicated with the nucleocapsid being contained within an envelope along with other structures that allow the virus to function.
