Evidence against use of bacterial amino acid sequence data for construction of all-inclusive phylogenetic trees.

摘要: Abstract It has been proposed that phylogenetic trees, intended to show divergence of eukaryotic protein and nucleic acid sequences, be extended include those from bacteria. However, we have compared the amino sequences 18 most divergent mitochondrial cytochromes c with bacterial c2 found average percentage difference between these was not significantly greater than among alone. The large discontinuities in physical-chemical properties recognized prokaryote eukaryote render it highly improbable members two classes should no more different one another either class alone, assuming sequence differences can accurately reveal evolutionary divergence. Instead, propose approach a limit change considerably less for comparison random sequences. This presumably is determined by structure/function relationship. When homologous reached such limit, convergence or back-mutations parallel mutations become as frequent mutations. As diverging proteins this steady-state condition, longer reflect numbers resulting substitution therefore species cannot positioned on tree. Insertions deletions are reversible substitutions and, provided they well-documented, might reliable indicators relationships. Nevertheless, suggest data available do permit construction all-inclusive trees. Comparisons rRNA trees similar restrictions apply use data.