Direction of Translation and Size of Bacteriophage phiX174 Cistrons

Translation of the bacteriophage X174 genome follows cistron order D-E-F-G-H-A-B-C. To establish this, the position of a nonsense mutation on the genetic map was compared with the physical size (molecular weight) of the appropriate protein fragment generated in nonpermissive cells. Distances on the X174 genetic map and distances on a physical map constructed from the molecular weights of X174 proteins and protein fragments are proportional over most of the genome with the exception of the high recombination region within cistron A.