Re: Good Mutations.

Moorad Alexanian (alexanian@UNCWIL.EDU)
Wed, 03 Dec 1997 13:44:32 -0500 (EST)

At 03:52 PM 12/2/97 -0600, R. Joel Duff wrote:
Moorad wrote:

>>I am not sure I understand. Is it possible that the bacteria have a sort of
>>bell-shaped curve of characteristics that determine what the bacteria is and
>>by means of environmental changes we can select the parts of the bell-curve
>>which we desire. Sort as animal breeding. Do we indeed have to talk of
>>mutations? Can we tell at the molecular level? What makes us say that we are
>>dealing then with the same bacteria?
>I think there is much less room for phenotypic variation in this case.
>Usually in such an experiment one plates bacteria onto a media and picks
>bacteria from a single colony. It seems safe to assume that all the
>bacteria in that colony came from a single bacteria. One then grows
>bacteria from that single colony up in some liquid media and then plates
>out several billion bacteria onto a different media (in this case higher
>salt concentration). Only a few of the millions/billions of bacteria may
>manage to survive. Since these bacteria all came from a single bacteria at
>one point we are definitely dealing with the "same bacteria." Rather than
>selection on a bell shape curve of characteristics due to inherent
>variation, it is more likely that the ability to survive on the salt media
>is due to a point mutation of some type that enables the bacteria to
>acquire an enhanced ability to deal with a high salt environment. Hope
>that helps.

In summary, from a particular kind of dog, say a chihuahua, we cannot ever
get a Saint Bernard. Is that your argument?


p.s. BTW I spent 2.5 years at the physics department of SIU.