December 11, 1973
Dear Bernie:
The gels, especially cylindrical ones, are fine. The agarose run clearly indicates that both JC and BK have short DNA, i.e., defectives. Presumably, these had not been recently plaque-purified. (We have been using agarose electrophoresis to detect and isolate deleted genomes.) This also accounts for the many minor bands after Hin A, B, C+D, E+F, G, H, I, J, K. Presumably failure to separate C and D, and E and F is due to the gradient gel; we use straight 4 percent acrylamide. The major point is well made.
For further work on the DNA, you should plaque JC and BK serially twice and pick a plaque each time from a dish containing <5 or so plaques. Grow stock from the plaque. In my experience, a plaque aspirated with a Pasteur pipette has several thousand pfu's.
With best regards,
Sincerely,
Daniel Nathans
P.S. As I mentioned to you earlier, Theresa Lee, in my lab, had also found that BK DNA (from Ken Takemoto) gives a totally different Hin digest than SV40.