laws of physics.” Delbriick had set to work on physical mechanisms in
genetics in part because of his interest in this possibility, as originally
articulated by Bohr.
Delbriick, incidentally, had also been inspirational to Watson and
Crick’s pursuit of DNA’s structure. Indeed, when the crucial insights
about the double helix had been attained, before their paper to Na-
ture had even been written, one of the first people to whom Watson
wrote to tell of the discovery was Max Delbriick, who by that time had
moved to the biology faculty at Caltech.
At least with respect to the physical basis of heredity, no impasses
have been encountered and no expanded scientific framework has
been needed. Indeed, quite to the contrary, the description of the
structure of DNA, the genetic code, and the processes of gene tran-
scription and translation are sufficiently simple that they are now
taught to children in elementary school. As Delbriick put it many
years later:
Nobody, absolutely nobody, until the day of the Watson-Crick structure,
had thought that the specificity might be carried in this exceedingly
simple way, by a sequence, by a code. This dénouement that came then
—that the whole business was like a child’s toy that you could buy at the
dime store—all built in this wonderful way that you could explain in Life
magazine so that really a five-year-old can understand what’s going on.
That there was so simple a trick behind it. This was the greatest surprise
for everyone.And there you have it, in outline at least—a beautiful saga in
twentieth-century science. The physical nature of the gene and the
subsequent understanding of mutations as nucleotide changes in the
DNA sequence provided a mechanism for the generation of variation
upon which selection could operate. Darwin’s ideas on variation and