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remove all transforming activity, such as bleach or acid or perhaps dry 
heating, and waste materials that have to be disposed of should be inciner- 
ated, waste material such as gels or plastic equipment that is thrown away. 
Autoclaving is not a satisfactory method of getting rid of transforming DNA. 
In the slow cooling process, in the cool down of the autoclave, DNA can reas 
sociate to an active double-stranded form. Once again, that is a classic 
experiment that was done on a bacterial transformation system. 
That is all. 
DR. FREDRICKSON: What about DNAase? Isn't that the best of all? 
DR. CHILTON: It is expensive, though, but yes. 
DR. FREDRICKSON: Mr. Hutt. 
MR. HUTT: Can I just make sure that you are not suggesting that it not 
be done at PI, you are simply suggesting that the Guidelines be a good deal 
more explicit about what can and can't be used in order to de-activate it, 
or whatever? 
DR. CHILTON: That is correct, yes. 
MR. HUTT: All right. 
DR. FREDRICKSON: That is correct. It was intended not to require the 
PI, but there would be a similar inactivation, and it was felt not necessary 
to spell it out precisely in the Guidelines as to what you would use. 
Dr. Zaitlin. 
DR. ZAITLIN: I am not sure I know why the containment level was raised 
but I think one of the problems here was that plant pathogens were sort of 
caught up in a general discussion where they were classified as Class 2 
agents on the basis of hazard, and really we had no rational basis for decid 
ing this. In the same letter to which you refer these four gentlemen have 
suggested, at least for plant pathogenic bacteria, that we can put them 
into three categories. I think for the future, if it can be done at all, 
and I am not sure that this is so, we might try to assess the hazards of 
plant pathogens including fungi and viruses. 
DR. FREDRICKSON: We will circulate the letters which have just been 
referred to. They came in only yesterday, and I haven't seen them either, 
but we will try to get copies to you tomorrow. 
DR. CHILTON: It strikes me that really there is such a small number of 
experiments of this type going on, that the most reasonable way to proceed 
at this point might be to do it on a case by case basis, and in that case it 
would be very nice if it were explicitly mentioned in the new Guidelines 
what the containment level appropriate for cloning the Agrobacterium Ti 
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