Figure 1.

Schematic of an orthologous protein phylogeny and the null hypothesis (Ho) of a constant relative rate of protein evolution. Comparison of multiple orthologous proteins is predicted to reveal a constant relative rate of evolution. This should be manifest as an approximately constant ratio of phylogenetic branch lengths (bold lines) bA/(bB + bC). The branch lengths were calculated using the evolutionary distances (dashed lines) between the proteins from three species (dAB, dAC, dBC) as described in Materials and methods.