Having a generic dictionary definition is nice and dandy. However, in the
present context, the term 'homology' has a much more specific meaning: it
pertains to the having (or not) of a common ancestor. Thus, it is a binary
concept. (*)
A useful paper about homology and percentage sequence identity (and structural
similarity) is Rost, 1999: http://www.ncbi.nlm.nih.gov/pubmed/10195279
--dvd ftw ;-)
(*) For instance, when applied to fictional characters, Luke and Leia are
homologous since they share a common ancestor in Mr Vader. See: Vader, D.
(1980). "No, *I* am your father." Star Wars 5, and: Vader, D. (1983).
"Especially for... sister." Star Wars 6.
On Fri, 5 Dec 2008, Dima Klenchin wrote:
to models built on low-homology structures.
since i'm currently preparing my bioinformatics lectures for next week's
teaching, i might as well be a Besserwisser and point out that homology,
much like pregnancy and death, is a binary concept. i'm sure artem knows
this and simply mistyped "low sequence identity"
Well, although it is off-topic:
Random House Unabridged Dictionary
Homologous
1. Corresponding or similar in position, value, structure, or function.
So if you insist that homologous is a binary concept then you should be able
to come up with the exact boundary between what's homologous and what's not.
What is it? 10% sequence identity? Less? More? Because if such a boundary
cannot be defined then everything can be homologous to everything - it's all
in the eye of the beholder. And if so, then the binary concept of homology is
either meaningless or incorrect.
Ergo: arguing about definitions of terms used to describe continua is not
very productive in science (cf. "species", "sea/ocean", "hill/mountain").
Dima
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Gerard J. Kleywegt
[Research Fellow of the Royal Swedish Academy of Sciences]
Dept. of Cell & Molecular Biology University of Uppsala
Biomedical Centre Box 596
SE-751 24 Uppsala SWEDEN
http://xray.bmc.uu.se/gerard/ mailto:[EMAIL PROTECTED]
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