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DR. BROWN: Can I ask you and Paul a direct question? Would you advise 
that these guidelines should stipulate that, using this new methodology, 
that physical or EK regulations can be reduced by one notch? 
DR. SINGER: I would certainly hope that with an evaluation of those 
methods, that precisely that sort of thing would happen. 
DR. BROWN: What kind of evaluation would you have in mind? 
DR. FREDRICKSON: Dr. Berg would reply to that cross-examination. 
DR. BERG: Only on technical grounds. Using that technique of screen- 
ing, you know what you can do is you can work with micro-colonies which, 
as you say, you need not pipette, and you can screen large numbers to look 
for a clone which contains a sequence that you want. 
It may also, and often will, contain sequences that you know nothing 
about . 
DR. BROWN: Along with the one you want. 
DR. BERG: Yes, along with the one you want. 
The second step is that you now have to pick the clone which you have 
identified and you must grow it up in order to get the DNA you want. So 
it is not now — it is passed from a micro-colony on a filter to something 
where you have to grow it up and culture it, centrifuge it, collect it, 
and so on. 
DR. BROWN: Paul, may I respond? 
DR. BERG: No, let me finish. 
DR. BROWN: I am sorry. 
DR. BERG: All the procedures which have been known to, in fact, 
generate the kinds of aerosols and possible contaminations that we know 
we are talking about. 
So the fact that you have identified the clone on a filter has not 
ended the experiment at that point. 
DR. BROWN: Now, can you explain to me, then, how one would ever 
characterize a clone? 
DR. FREDRICKSON: I wonder if we are not bogging down. Dr. Brown. 
I don't want to interrupt that line, but I want to go in order. 
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