SaC: "directed mutations" articles reviewed

[Lisa Rogers <eqwq.lrogers@xxxxxxxxxxx>]

There was this little thread on SaC, which reminded me of a thread we
once had on marxism, so, in case anybody's interested...

Forwarded Mail received from: Lisa Rogers

      Date:  12/14/1995  09:14 pm  (Thursday)
      From:  Lisa Rogers
        To:  STATE-DOMAIN.WPSMTP("SCIENCE-AS-CULTURE@xxxxxxxxxxxxxxxxx
             ")
   Subject:  SaC: "directed mutations"

I know of at least two people on this list that said they were
interested in this thread specifically.  I found it interesting and
challenging, so I went to the library and read some stuff.  I report
on two articles.

Foster and Cairns, 1992 "Mechanisms of Directed Mutation", Genetics
131:783-789.

F+C state that "Spontaneous mutants arise among nondividing
populations of E. coli in apparent response to selective conditions."
This is their definition of directed mutation, they have both
published previously on their research which provided some evidence
for that statement.  It is the starting point of the further research
reported in this paper.  This is one of the more recent works
investigating and summarizing the evidence and lack thereof for
specific proposed molecular mechanisms by which directed mutations
might occur.  F+C hold that most hypotheses about the molecular
method of occurence have been falsified by experimental results.  The
paper ends with their new hypothesis, which appeared to be consistent
with available data, but still remained to be tested.


Lenski and Mittler 1993 "The Directed Mutation Controversy and
Neo-Darwinism", Science 259:188-194

I reproduce most of their abstract here:
"According to neo-Darwinian theory, random mutation produces genetic
differences among organisms whereas natural selection tends to
increase the frequency of advantageous alleles.  However, several
recent papers claim that certain mutations in bacteria and yeast
occur at much higher rates specifically when the mutant phenotypes
are advantageous...  Ciritics contend that studies purporting to
demonstrate directed mutation lack certain controls and fail to
account adequately for population dynamics.  Further experiments that
address these criticisms do not support the existence of directed
mutations."

L+M present this as a review article, which it is, but let me also
note that they are part of the opposition in a sense, their own work
and previous publications have been challenging the existence of
directed mutations, by designing experiments and data analysis
methods intended to avoid what they see as flaws in the work of
Cairns, Hall, Foster, etc.


Now, I realize that I am not analyzing science as culture, per se, in
this post.  I propose that it is related to list-topic/s anyway.

1.   I want to call into question the view that "directed mutation"
is a "FACT", scientific or otherwise,

2.   which relates to the facticity thread as well as the DM thread.

3.   This is an example of science which could be further analyzed
here,

4.   where some interest has been shown in the topic.

Come to think of it, after the facticity discussion, it's a little
ironic that some members of SaC previously seemed to accept the
"fact" of directed mutation.   I wonder what might be the cultural
explanation for that.

Hoping this offering is found relevant,
Lisa



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