Claudia Stanny asked the following interesting question: > I have often seen data cited about the percentage of genetic > material that is common between humans and other primates > (chimpanzee, gorilla,etc.), but I have never seen such a figure > for humans and dogs. Anybody out there know how large the > percentage of common genetic material is for humans and dogs? > (I haven't had any luck searching the genome web sites.) Now I haven't a clue about the answer to this, but I do have a friend and neighbour who happens to be an accomplished researcher in molecular biology. So I asked him whether this question could be answered for a variety of species, whether it was a meaningful question, and also appended Claudia's specific query. I also speculated that there might be a web site somewhere in which you could type in species A and species B, and get a percentage DNA shared as output. The short answer is no. Here, with his permission, is his response in full. Dear Stephen, I am not aware of any program which could make a comparison between two entire species. NCBI has a web site which shows the homology between human and mouse, but only an expert could understand it. Asking for a global homology between two species, based on genomic sequence, is not an invalid question, but is not very informative either. The question of homology is in fact a very complex, multileveled notion. For example, the ubiquitin protein is nearly 100% identical in protein sequence (and totally identical in function) among all eukaryotes (from yeast to man), so we are tempted to conclude that sequence is essential to maintaining function. Wrong! There are numerous other examples where sequence has completely diverged, yet the three dimensional structure of the molecule was maintained and so was function. So lack of sequence homology is not a stringent criteria in functional terms - and ultimately we are concerned with function. Indeed, we are now more concerned with structural homology. Life is complex! No simple answers. Hope this is of some help. Joe Joseph M. Weber Fac. Medicine, Univ. Sherbrooke, Sherbrooke, Quebec, Canada
