IUBio Biosequences .. Software .. Molbio soft .. Network News .. FTP

homologue vs ortholog

Geeta Bharathan fzyenath at dale.ucdavis.edu
Tue Sep 3 19:02:12 EST 1996


Lee Meisel (meisel at AESOP.RUTGERS.EDU) wrote:
: 
: Recently when reading a variety of papers I have seen ortholog and
: homologue used in similar context.  I'm pretty sure there is a
: difference between ortholog and homologue but am unsure of what that
: difference is.  Unfortunately, ortholog is not in the Webster's
: dictionary or in a genetic dictionary we have available.  Could someone
: please explain the difference between ortholog and homologue, as well as
: the criteria necessary to define a sequence as an ortholog or a
: homologue.  
: 
The terms orthologue and paralogue were introduced by Fitch in the 1970's, I
believe. He used the terms to describe different kinds of duplicated
genes--duplications within the genome of a species lead to paralogous genes;
duplications due to speciation lead to orthologous genes.

I believe that molecular biologists often use functional/other experimental
criteria to determine orthology. However, this is an evolutionary concept,
and the best way, IMHO, to deal with this question is through phylogenetic
analysis. Orthologous genes (of different species) will be most closely
related and form a group; paralogous genes (different versions of a gene
in the same species) will be separated on a tree of relationships.

-----------------------------------------------------------------------
Geeta Bharathan                    e-mail: grbharathan at ucdavis.edu
University of California           phone : (916) 752-9007
Agronomy & Range Science           fax   : (916) 752-4361
217 Hunt Hall
Davis, CA 95616
-----------------------------------------------------------------------



More information about the Arab-gen mailing list

Send comments to us at biosci-help [At] net.bio.net