"Lamarkian" mutations - how does one descern?

John E. Stacy johnest at ulrik.uio.no
Mon Apr 12 07:58:34 EST 1993

I was browsing through this newgroup a while back and saw a few 
contributions on "purposful" mutation (I guess "Lamarkian" wasn't a
good term, but it seems to come up in this connection). Today I was 
reading Scientific American, and saw a few paragraphs describing, I
assume, "induced" reversion to lactose metabolism; i.e. bacteria on 
lactose rich (glucose poor) plates mutated to lactose metabolism at
a higher rate than they "should" have. As you can see, I'm pretty 
sketchy on this subject, and don't even remember who did the experiment.
But my question is pretty simple: what are the essential nuts and bolts
of this type of experiment? What control can be run to show that the 
mutation rate is in fact higher in the presence of lactose? To me it 
seems that if you have lactose in the start medium, you are simply
selecting for lac+, not inducing it.
John Stacy
University of Oslo

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