The Mechanics of Inheritance
THE MEANING OF THE GENE
BY ROWLAND H. DAVIS
"And yet," said Legrand, "the solution is byh no
means so difficult as you mnight be led to imagine
from the first hasty inspection of the c/hracters.
These characters, as anyone milght readily guess,
form a cipher-that is to say, theyI convey a
meaning... I made up myn mind, at oice, tlatt
this was of a simple species-such, how'ever, as
would appear, to the crude intellect of the sailor,
absolutely insoluble without the key."
E. A. Poe. The Gold Btug
T O MANY PEOPLE, the fact that organisms reproduce their own kind seems
so natural that any further questions
on genetic mechanisms seem academic. But
confronted with the small differences, or
mutations, among the members of a biological species, and with the fact that these
differences are the basis of organic evolution, they must pause and reflect upon the
nature of any living system. By pursuing the
thought that mutations are possible, they will
infer, as did biologists, the existence of a
body of information-information which lies
in every cell of which an organism is made,
and which may be subject to errors of duplication as it is passed from an organism
to its descendants. This body of information, we now know, is composed of genes--
mutable, duplicating entities which are in
some manner able to specify the characters
of the organism which inherits them. The
weakness of these conclusions is that they
merely state a consistent set of relationships;
they do not tell us what, in fact, the physical nature of the system is. And since many
falsehoods can be consistent, a close apROWLAND H. DAVIS is a native Bostonian and a
Harvard graduate (A.B. '54, Ph.D. '58). He held
fellowships at Harvard, 1954-58, and in 1958-60
was a research fellow of the National Science
Foundation at California Institute of Technology.
He came to this university in 1960 as Assistant
Professor of Botany.
proach to the truth may be made only when
the relationships are consistent also with
the physico-chemical system in which they
prevail.
A new field within the life sciences has
emerged recently which deals with this
problem. It has been called Molecular
Genetics, among other things, and by borrowing techniques from many fields, notably
chemistry and physics, it has given us quite
a clear picture of the chemical facts of life.
Specifically, it has thoroughly elaborated the
nature of the "master molecule," the gene,
upon which all of life ultimately depends.
The problem is one which involves an intriguing cryptography, used in the recent
deciphering of the genetic "code" for life's
many forms and functions. It is a code, as
Poe says, which any simple sailor would
think insoluble without the key. The story
of the genetic code, like Poe's story, is far
more interesting in the deduction of the key
than in the meaning of a given message.
N THE ORGANIC WORLD, there are a number of important classes of large molecules, or macromolecules, which can be
characterized as long chains of similar units.
The two classes of macromolecules of
greatest interest are proteins, made up of
amino acid units, on the one hand, and the
nucleic acids, made up of nucleotide units,
on the other. Our ultimate goal is to describe these large molecules, their functions,
and the relationship between them. Our
interest stems, first, from the knowledge
that proteins seem to be the primary agents
of all transformations-chemical and developmental-that characterize living systems. Second, nucleic acids appear to be the
source of information required for the
manufacture of different proteins, as well
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