Origins of the viral world

The numbers of additional steps (S) required to force molecules into monophyly were calculated based on class (class I and II tRNAs) and organismal (three superkingdoms of life or viruses) constraints using MP analyses of combined tRNA structure and sequence data. The length of the most parsimonious trees derived from the combined data set was 10,083 steps. Each constrained group is given in parentheses and groups of tRNA molecules are indicated by superkingdoms of life (Archaea, Bacteria, and Eukarya) or viruses. Both chloroplast and mitochondria tRNAs were included in Bacteria. A = Archaea, B = Bacteria, E = Eukarya, V = viruses, VB = viruses associated with Bacteria, VE = viruses associated with Eukarya. CH, competing hypothesis.