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Because most newly arising mutations are neutral or deleterious, it has been
argued that the mutation rate has evolved to be as low as possible, limited
only by the cost of error-avoidance and error-correction mechanisms. But up
to one per cent of natural bacterial isolates are 'mutator' clones that have
high mutation rates. We consider here whether high mutation rates might
play an important role in adaptive evolution. Models of large, asexual,
clonal populations adapting to a new environment show that strong mutator
genes (such as those that increase the mutation rates by 1000-fold increase)
can accelerate adaptation, even if the mutator genes remains at a very low
frequency (for example, 10^-5). Less potent mutators (10 to 100-fold
increase) can become fixed in a fraction of finite populations. The
parameters of the model have been set to values typical for E. coli
cultures, which behave in a manner similar to the model in long-term
adaptation experiments.
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Another article appearing in Science (276:1665-1669, 1997) entitled,
"Structural insights into the evolution of an antibody combining site" is
also informative and relevant to recent discussions here. This paper is
also the subject of a Perspective article on evolutionary chemistry that can
be found in the same issue. The paper begins to address the general
question of how could enzymes evolve.
One of the criticisms Mike Behe has raised has to do with the dearth of
information about the evolution of complex molecular systems. It seems to
me that this area is beginning to be examined by molecular biologists and
these papers support this contention.
Science is a process and the science of evolution is undergoing this
process. The fact that critical answers to some of the questions raised by
Behe, and others on this reflector are not available is not a sign of the
death of the evolution model. Indeed, the fact that evolution scientists
are beginning to explore new areas of molecular and developmental biology
indicates that the intellectual process is healthy and not stagnant.
Cheers,
Steve
_________________________________________________________
Steven S. Clark, Ph.D . Phone: 608/263-9137
Associate Professor FAX: 608/263-4226
Dept. of Human Oncology and Email: ssclark@facstaff.wisc.edu
UW Comprehensive Cancer Center
CSC K4-432
600 Highland Ave.
Madison, WI 53792
"It is the glory of God to conceal a matter, but the glory of kings to
search out a matter." Proverbs
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