In 1966, geneticist and Nobel laureate George Beadle and his wife Muriel published a laymen's guide to genetics titled
"The Language of Life: An Introduction to the Science of Genetics." In this 1965 letter, Kornberg responded to Muriel
Beadle's request for details of his DNA synthesis work to include in the book.
Number of Image Pages:
2 (112,121 Bytes)
1965-02-04 (February 4, 1965)
Original Repository: Stanford University Libraries. Department of Special Collections and University Archives. Arthur Kornberg Papers
Reproduced with permission of Arthur Kornberg.
Medical Subject Headings (MeSH):
"Creating Life in the Test Tube," 1959-1970
Letter from Muriel Beadle to Arthur Kornberg (January 26, 1965)
Letter from Muriel Beadle to Arthur Kornberg (February 14, 1965)
February 4, 1965
I enjoyed hearing from you and will do the best I can to describe the circumstances of the experiment you ask about. I assume
you are curious about how we found a copolymer containing adenine and thymine in the absence of added primer, a synthesis
we have called de novo formation of dAT polymer. Dr. Howard Schachman, of the University of California in Berkeley, spending
his sabbatical year with us at Washington University in St. Louis, Dr. Julius Adler and Dr. I.R. Lehman, postdoctoral fellows,
shared in this experiment. Prior to the fall of 1957, we had measured the primed synthesis of DNA using optical and chemical
methods. We had run suitable controls but the incubation periods never exceeded two to three hours.
At this time we decided to measure DNA synthesis by a viscometric technique. We expected the synthesis of new DNA to be accompanied
by an appropriate increase in the viscosity of the solution. This is indeed what we found. A control was included in which
one of the four triphosphates was omitted; fortunately, as it turned out, the omitted triphosphate was dGTP (guanine). Another
fortunate circumstance was that measurements in the viscometer were continued up to and beyond four hours. We observed no
change in the control tube for the first four hours but then during the next two hours there was an extremely rapid and extensive
increase in viscosity. That evening we thought of several possible sources of error: inadvertent addition of the triphosphate
(dGTP) which we had intended to omit, bacterial growth, some technical anomaly in that particular viscometer. The next day
the experiment was re-run and we were able to eliminate each of these possible sources of error. We established that the
development of viscosity occurring after a 4-6 hour lag period took place even though the primer DNA was also omitted. The
day after that we were able to show that all that was necessary to obtain this unprimed reaction were the two triphosphates
dATP (adenine) and dTTP (thymine) in addition, of course, to the enzyme and Mg++. Thereafter it was easy to establish that
a high molecular weight copolymer of these two nucleotides (A and T) is the product of this unprimed or de novo synthesis.
As you can see, the experiment was not set up to determine whether synthesis could occur without a primer but rather as a
routine control showing the requirement for all triphosphates (A, T, G and C). We had many times before attempted to observe
whether synthesis could occur without a primer but had never followed the reaction for as extended a period of time. (It
turns out, too, that when taking samples at less frequent intervals of time, as one does with isotope incorporation assays,
it is relatively easy to miss the synthesis of this copolymer using the relatively crude enzyme preparations available to
us at that time. These crude preparations have a nuclease that destroys the polymer rather rapidly.)
This account will diminish your estimation of our insight in finding de novo DNA synthesis. On the other hand, this experience
chalks up some points, as if more were necessary, for the scientific discipline of demanding proper controls, including the
use of a variety of methods, to check the nature and authenticity of a reaction.