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<DIV><FONT face=Arial size=2>That is a good question.</FONT></DIV>
<DIV><FONT face=Arial size=2>Concerted evolution (various mechanisms) keeps the
copies the same as each other. The copy number changes over time and no
one copy in one species is considered the orthologue of a copy in another except
when the copy number is small and individual copies are identified by
position. </FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>The possible mechanisms that allow concerted
evolution include unequal crossing over (you have tandem repeats that match up
incorrectly at meiosis; these swap between chromosomes and some are gained and
some lost; this repeated sampling creates uniformity over time) and gene
conversion (transcript of one gene "corrects" the sequence of
another).</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Des</FONT></DIV>
<DIV> </DIV>
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<DIV>"Jason S" <<A
href="mailto:jas2339@yahoo.com">jas2339@yahoo.com</A>> wrote in message <A
href="news:mailman.1073.1148420085.16885.mol-evol@net.bio.net">news:mailman.1073.1148420085.16885.mol-evol@net.bio.net</A>...</DIV><BR>
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<DIV>Hi there,<BR><BR>Here's a newbie question: if there are hundreds of
copies of ribosomal genes in a genome, how can we know which copy we are
working on? and how can we be sure that they are orthologous among
species?<BR><BR>With best regards,<BR><BR>Jason </DIV>jas2339@yahoo.com
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