At 6:34 AM -0500 11/7/00, alex wrote:
Try Henderson's dictionary of Biological terms- a gem. Homologues
have resemblance in structure and origin, not necessarily function.
This word has been co-opted by we biochemists to mean similarity in
structure and function, which is NOT in accord with the true
biological meaning of the word.
Hence, we now see reference to orthologues, genes (and gene
products), which are derived from a common ancestor and hence likely
to have similar function.
Paralogues arise from gene duplication events and result in
somewhat similar genes (and products) which may have different
function. A very interesting example of a family of vertebrate
neuropeptides with this relationship is the corticotropin releasing
factor/sauvagine/urotensin I/urocortin family. Sauvagine was
discovered first, and felt to be the homologue of CRF in frogs.
Urotensin I was thought to be the homologue of CRF in fish. However,
genes encoding CRF were pulled in fish and frogs, prompting the
search for a sauvagine/urotensin I "analogue" in rats. This led to
discovery of Urocortin. So urocortin, sauvagine, and urotensin I are
orthologous, all the forms of CRF are orthologous, but these are two
families of paralogues.
>Orthologue, paralogue and homologues (and possibly other logs) have been
>used by biologists and it is very unclear to me what the differences are
>between some of these ...logues.
>
>Best wishes,
> alex
David
-- David A. Schooley Dept. of Biochemistry/330 Univ. of Nevada Reno, NV 89557 schooley@unr.edu tel: (775) 784-4136; fax (775) 784-1419 NOTE NEW AREA CODE: Mandatory after 5/15/99
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