🚀 go-pugleaf

I'm supposed to be able to understand all this, but I was wondering if
anyone could summarise the articles on adaptive mutation in the April
21, 1995 issue of Science.  

I know that's too broad, so I'm going to attempt ask specific
questions here.  Forgive my ignorance:

(i) What does it mean to say (in the news and views section) "strains
ontaining lacI-Z33 display delayed kinetics of Lac+ colony appearance
when plated on lactose medium, indicating that many more frameshit
events occur after selection than during prior growth, that is,
adaptive mutation." (p373)

(ii) I do understand, after reading all the papers, clearly how they
can make the claim "90 to 95% of the revertants present on the plates
seem to be the result of mutations that occur on the plate." (p418)

(iii) I also don't understand the whole transfer of plasmid from
streptomycin sensitive to streptomycine resistant bacteria experiment.

There are others, but to me it is not clear what they mean by
"selection-induced-reversion".  I suppose it'll come after re-reading
and crosschecking all the terms, but I was wondering if someone could
explain it in simpler terms.  What is happening exactly?

Thanks a lot!

--Ram
                                          I      on a big Trp
Ram Samudrala                            / \ 
ram@elan1.carb.nist.gov                 |   |
Check out the TWISTED HELICES band       \ /
page at http://www.wam.umd.edu/~ram/th  __/