In Pursuit of the Gene

230 ¨ X-RAYS
consensus, which included every major figure in genetics save Willem
Johannsen, who was never to concede the point. But Bateson still refused
to give his blessing to the theory of crossing over, which was the lynchpin
of the whole argument, arguing that it was still too early to “contemplate
so concrete and material a picture of the mechanism of crossing-over.” 31
On the same day that Bateson spoke before the Society of Zoologists,
Muller addressed the American Society of Naturalists. 32 In his lecture, Muller
touched briefly on the current state of the chromosome theory, including
the finding that the two larger of the Drosophila chromosomes each contained
hundreds of genes whose locations could be determined by crossing
over, which he took as established facts. But the point of his lecture, which
had an almost hallucinatory quality about it, concerned his bold and strikingly
original discussion of the nature of the gene.
He began by observing that the most distinctive property of genes was
that they were capable of reproducing themselves. More exactly, a gene
had the ability to convert material from the protoplasm of the cell into an
exact copy of itself. While there were many examples of complex biological
molecules (enzymes) that catalyzed chemical reactions, the strange thing
about genes was that of all the possible reactions genes might have catalyzed,
they affected just those that resulted in the production of molecules
with their own complex structure. But this “autocatalytic” property of
genes was not even the most surprising aspect of the situation, Muller insisted.
The truly astonishing thing was that when the structure of a gene
changed due to an entirely random mutation, the altered gene was nonetheless
still faithfully reproduced. On the face of it there was no obvious
reason why a change in the gene’s structure that resulted in a change in its
function would simultaneously alter the gene’s autocatalytic function in
just the precise way that would result in the new variant of the gene being
reproduced.
Without mentioning Bateson by name, Muller next turned to the subject
of Bateson’s plenary address of the night before. “It is commonly said
that evolution rests upon two foundations—inheritance and variation; but
there is a subtle and important error here,” Muller declared, echoing