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.
Jordan et al. Genome Biology 2001 2:research0053.1 doi:10.1186/gb-2001-2-12-research0053