Homology/similarity/identity: proper usage.

frist at ccu.umanitoba.ca frist at ccu.umanitoba.ca
Fri Feb 1 16:00:54 EST 1991

I think it may be useful, at this point in the discussion, to construct a
chart relating the terms under discussion. Comments, anyone?

                When two structures share common substructures,
                those common substructures are said to be identical.
                 Similarity is the degree to which two structures share
                 common substructures.
               |                                           |
           HOMOLOGOUS                                  ANALOGOUS
    Similarity due to common                 Similarity due to convergent
          ancestry                                     evolution
               |                     |
           ORTHOLOGOUS           PARALOGOUS
    Homologous structure with  Homologous structure with
    with conserved function    divergent function
Brian Fristensky                | "The important thing is to develop the
Dept. of Plant Science          |  capacity to see one kernel that is differ-
University of Manitoba          |  ent, and make that understandable. If it
Winnipeg, MB R3T 2N2  CANADA    |  doesn't fit, there's a reason, and you find
frist at ccu.umanitoba.ca          |  out what it is."
Office phone:   204-474-6085    | Barbara McClintock, from A FEELING FOR THE
FAX:            204-275-5128    | ORGANISM by Evelyn Fox Keller 

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