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ortholog and paralog

pryor at mail.teclink.net pryor at mail.teclink.net
Thu Feb 13 22:51:25 EST 1997

duret at acnuc.univ-lyon1.fr (Laurent Duret) wrote:

>   "Where the homology is the result of gene duplication so that
>   both copies have descended side by side during the history of 
>   an organism, (for example, alpha and beta hemoglobin) the genes
>   should be called paralogous (para = in parallel). Where the 
>   homology is the result of speciation so that the history of the
>   gene reflects the history of the species (for example alpha 
>   hemoglobin in man and mouse) the genes should be called orthologous
>   (ortho = exact)."
OK, fine. But how do you know the beta globins are homologs? Could you not 
have duplication of beta globins in an ancestral species, with one lineage 
maintaining functionality in one and the other the other..with genomic 
rearrangements, etc. how could you tell..or due you assume that there was 
no duplication of beta globins.. an assumption which appears to be 
absolutely incorrect.

How could you ever possibly know that "a gene reflects the history of a 
species" without making a prior assumption that the gene you want to 
"reflect the history of the species" does reflect the history of the 

Robert Hamilton

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