Ninety-five percent of this protein is collagen, which was discarded. The remainder was sorted according to protein size by gel electrophoresis, and each purified protein type was then laboriously tested in mice for its capacity to induce new bone growth. No other known substance, after all, could produce new bone. When a scientist identifies a new protein or gene sequence, he punches it into a computer database to learn whether it truly is new and whether it is similar, or homologous, to anything else. Homology provides important and sometimes unexpected clues to a molecule's function and evolutionary provenance.
Sequences drift over time.
All allow a certain amount of leeway, but crucial features cannot change without losing their function. Very important or fundamental sequences are generally held within strict bounds. Dpp is not a human gene. It is found in Drosophila melanogaster, the fruit fly. Fred Kaplan says.