Path: utzoo!utgpu!watserv1!watmath!att!pacbell.com!ucsd!usc!samsung!sol.ctr.columbia.edu!caen!news.cs.indiana.edu!ariel.unm.edu!nmsu!opus!owhite From: owhite@nmsu.edu (smouldering dog) Newsgroups: bionet.molbio.evolution Subject: Re: Homology/similarity/identity: proper usage. Message-ID: Date: 31 Jan 91 21:20:27 GMT References: <3824@gazette.bcm.tmc.edu> Sender: news@NMSU.Edu Organization: Computing Research Lab Lines: 34 In-reply-to: steffen@mbir.bcm.tmc.edu's message of 30 Jan 91 18:56:01 GMT In article <3824@gazette.bcm.tmc.edu> steffen@mbir.bcm.tmc.edu (David Steffen) writes: > I am again struggling with the proper use of the words "homology", > "similarity", and "identity" in comparing sequences. Specifically, we > have cloned and sequenced (a bit of) the rat homologue of the _lck_ > etc...... this is a topic worth discussing. my understanding is that when you are referring to a sequence that has _some_ nucleotides in a close approximation to another sequence you should say: sequence A has __% similarity to sequence B. alternatively you can say: sequence A has __% identity to sequence B. to refer to two sequences being homologous means they are a _strict_ (nucleotide for nucleotide) match. as in: the cDNA sequence to gene A is homologous to region X of the genomic clone of gene A. alternatively you can say: the cDNA sequence to gene A is identical to region X of the genomic clone of gene A. however, I am curious if the rest of the community agrees with the above usages of identity, similarity and homology. owen white -- owen white (owhite@nmsu.edu) -=-*-=-=-*-=-=-*-=-=-*-=-=-*-=-=-*-=-=-*-=-=-*-=-=-*-=-=-*-=-=-*-=-*-=-=-*-=- got my head on a pole (for better reception) -=-*-=-=-*-=-=-*-=-=-*-=-=-*-=-=-*-=-=-*-=-=-*-=-=-*-=-=-*-=-=-*-=-*-=-=-*-=-