molecular clocks

Tom Schneider toms at fcs260c2.ncifcrf.gov
Mon Sep 9 13:40:18 EST 1991


In article <1991Sep7.202039.6949 at news.yale.edu> RANBRUH at YaleVM.YCC.Yale.edu writes:
>It is important to distinguish between "mutation rate" and "rate of
>evolution" when discussing a molecular clock.

Nice distinction.

>RNA-based viruses, for example, these have rates of mutation which
>appear orders of magnitude greater than rates observed for other DNA-
>based organisms.

Along these lines, it is interesting that there are mutations of the T4 DNA
polymerase which DECREASE the rate of mutations in that phage!  (Could someone
post the reference if they know it?)  This implies that the rate is under tight
evolutionary control.  If times are tough, then the rate might be higher.  An
interesting example is the high rate of HIV mutation.  As I understand it, this
helps it to escape the host immune system...  Anyway, if rates are under
genetic control, the 'clock' becomes dependent on the particular organisms
studied and their history.

>B.H. Rannala
>Division of Evolutionary Biology and Ecology
>Biology Department
>Osborn Memorial Laboratories
>Yale University
>New Haven, CT 06511-7444

  Tom Schneider
  National Cancer Institute
  Laboratory of Mathematical Biology
  Frederick, Maryland  21702-1201
  toms at ncifcrf.gov



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