Thisisthedouble-stranded,covalentlyclosed,circularformofΦX174RFIDNA(supercoiled).ThemolecularweightofΦX174RFIis3.50 x 106daltonsanditis5,386basepairsinlength.ThevastmajorityofthemoleculesareRFI,andtheremainderareRFII,asdeterminedbyagarosegelelectrophoresis.