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DR. FREDRICKSON: Dr. Berg, do you wish to add to that? 
DR. BERG: I think it is fair to say, in spite of what Dave said, 
that there is not yet any concrete evidence of accurate expression of any 
eukaryote gene in a prokaryote. There is evidence of new products, poly- 
peptides, but the origin of those and how they are produced is not clear. 
What Ron Davis has found, in a paper which has just been submitted, 
is that it is possible that a DNA segment from a yeast can provide some 
functions which allow an Ej_ coli cell requiring histidine to grow in the 
absence of histidine. How it does it is quite obscure. So at the moment 
I think it is not clear that there is accurate expression of the genetic 
element in an .E. coli system in the way it is expressed in the host of 
origin. 
I think I tried to indicate that yesterday, and I think it is a ter- 
ribly important point in evaluation of this. But it also has another com- 
ponent, which if I can take another minute — 
DR. FREDRICKSON: By all means. 
DR. BERG: If we expect to benefit from this methodology in the sense 
in which I indicated yesterday, that is, to take genes from organisms, 
complex organisms and introduce them into simple organisms and hope to 
express them in that host, if expression is rare, we can assume it is pos- 
sible, but very rare, then we may of course not get the benefits that we 
are projecting. 
On the other hand, it is in _E. coli , and very likely only in E^. coli , 
at least for the very forseeable future, that we know enough about its 
genetic systems to hope to manipulate that inserted segment in such a way 
that it becomes translatable. That is, it is possible to imagine taking 
a segment out of animal cell, introducing it into an E^. coli , but not put- 
ting the appropriate signals, again by manipulating signals in front of it 
and in back of it to make it indistinguishable from a prokaryote gene, and 
ask the _E. coli now to express it and translate it as if it was one of its 
own. The hope of doing that with any new organism, the messiah of the 
future, I think is just so difficult to contemplate, I think the benefits 
are likely to come from our understanding of knowing _E. coli . The ability 
to protect ourselves also comes from our familiarity with E^. coli . To me, 
it seems that _E. coli is by far the organism of choice rather than going 
to look for some completely unknown organism which we will never — well, not 
never, but certainly only in the very distant future, hope to be able to 
manipulate to that extent. 
DR. FREDRICKSON: Thank you, Dr. Berg. 
DR. WRIGHT: May I make a comment, please? 
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