What gene do I use

What gene do I use - would not lead to regrouping taxa...

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What gene do I use ??: Depends on the taxa you are studying and the amount of divergence among them. Histones good for "macrosystematics", fibrinopeptides, mtDNA good for "microsystematics" or population level phylogenies. See fig. 17.15, pg. 489. Note problems with tree building from data: unequal rates and convergence . As if the choice of gene/protein were not a problem. What if different lineages evolve at different rates? Test for this with the relative rate test . Compare the paths from two different taxa to a third taxon. If the paths are the same: taxa are evolving at the same rate; if not: different rates. Extreme rate fluctuations are a problem; slight ones are not as they
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Unformatted text preview: would not lead to regrouping taxa (depending on how "slight" is defined) Convergence over long stretches of DNA is unlikely, although it has been reported for lysozyme. Another kind of "convergence" can occur due to the limited number of character states in DNA. Back mutations : e.g. A changes to T, T changes to C and C changes back to A. Could occur in one step or many. Maximal random divergence: 25% similarity Nonetheless molecular tools have allowed major leaps in our understanding of biological diversity: Bacterial evolution : three kingdoms, not five; Endosymbiont hypothesis , essentially proven; AIDS virus : rapid evolution is good for the virus, bad for us....
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