Presentation Speech by Professor T. Caspersson, member of the Staff of Professors of the Royal Caroline Institute
Your Majesties, Your Royal Highnesses,
Ladies and Gentlemen.
One of the most striking features in the development of science
during the past two decades is the rapid advance in the diverse
fields of biology. Here the tempo of progress continues to
quicken. The research contains a vast and complex material whose
major portion remains the business of specialists. The
observations they make in the laboratories of basic research are
apparently distant from the needs of the everyday world. But
again and again we discover how short the step is from these
basic findings to advances in medical therapy or diagnosis that
are of importance to all of us in our daily lives.
For an example we need turn only to the previous Nobel Prize in
Genetics, awarded to H.J. Muller
for his discovery that X-ray irradiation can change the genetic
material in living organisms. The discovery was made, and the
detailed analysis carried out, in a type of small fruit fly, and
at the time that the prize was awarded, perhaps gave the
impression that its greatest interest was in its contribution to
basic principles. Now, with the era of atomic energy upon us, we
all know that the genetic risks from the high-energy radiation
threatening man, belong to the things I just mentioned, of vital
and immediate importance to us all.
Experimental genetics is a branch of modern biology in which
progress has been especially rapid. The methods and points of
view of this and its allied disciplines are indispensable for
many fields of medicine today. This rapidly increasing importance
of experimental genetics and cell research is easily understood.
The research is now reaching towards the very elements of
heredity, the structures within each cell that control its life
and its behavior, and thus ultimately determine the development
of the whole organism. Now we begin to see what the fundamental
biological processes may be. That discoveries in this field have
consequences in many others is surely no surprise to any of
us.
The work of all three winners of the prize lies on this plane.
Their studies are concerned with the very basis of heredity and
the manner in which the genes function. That hereditary
characters are transmitted from parents to offspring via special
elements in the ovum and spermatozoon, the so-called genes, has
long been known. The organism that develops from the fertilized
ovum receives certain of the parents' characters through these
genes, and the genetic material in the fertilized egg, that is to
say, all these genes combined, determines the development of the
organism.
The cells that together constitute an organism as a rule contain
a complete set of genes characteristic of the species. In
ordinary cell division these are divided and subsequently
distributed equally between the two daughter cells. At
fertilization, the different genetic materials from two
individuals unite in the fusion of the egg and the sperm. The
result of the sexual reproduction is to provide offspring with
genes from both of their parents. In this way, individuals with
differing combinations of characters originate. And just herein
lies the biologic value of the sexual process, which can be
traced throughout practically the entire animal and plant
kingdoms. Without the renewal such a constant recombination of
characters involves, an animal or plant species would not be able
to survive the struggle for existence.
The characters, which are transmitted by the genes from
generation to generation, present a picture of bewildering
multiplicity. This very multiplicity of the genes' effects made
it difficult to attack experimentally the problem of their
structure and manner of functioning; it was impossible to trace
straightforward lines that could serve as a background for an
experimental study.
The situation was radically changed by Beadle and Tatum, who,
through a daring and astute selection of experimental material,
created a possibility for a chemical attack upon the field.
Circumstantial evidence pointed to a similarity of the genetic
mechanisms throughout the entire plant and animal kingdoms.
Beadle and Tatum selected as object for their investigations an
organism with very simple structure, a bread mold, Neurospora
crassa, which is far easier to work with, in many respects,
than the objects usually studied in genetics. It is able to
synthesize its body substances from a very simple culture medium:
sugar, salts, and a growth factor. When cultures of the mold are
exposed to X-ray irradiation, mutations - that is, changes in
individual genes - result as they do in other organisms. By
producing a large number of such mutations and by means of an
analysis of the material, which should serve as a model for
analytic research, Beadle and Tatum succeeded in demonstrating
that the body substances are synthesized in the individual cell
step by step in long chains of chemical reactions, and that genes
control these processes by individually regulating definite steps
in the synthesis chain. This regulation takes place through
formation by the gene of special enzymes. If a gene is damaged,
for example through irradiation-induced mutation, the chain is
broken, the cell becomes defective - and may possibly be unable
to survive. Even in the formation of comparatively simple
substances the steps in the synthetic chain are many, and
consequently the number of collaborating genes large. This
explains simply why gene function appeared to be so impossibly
complex. The discovery provides our best means of penetrating
into the manner in which the genes work and has now become one of
the foundations of modern genetics. Its importance extends over
other fields as well, however.
Especially valuable is the possibility it affords for detailed
study of the processes of chemical synthesis in the living
organism. In Neurospora material it is easy by means of
X-ray irradiation to produce quickly a large number of strains in
which the function of different individual genes has been
disturbed. By comparing these strains we are able to determine in
detail how the different stages of synthesis succeed one another
when the cell's substances are formed. Beadle and Tatum's
technique has become one of our most important tools for the
study of cell metabolism and has already yielded results of
significance to various problems in the fields of medicine and
general biology.
The successful results with Neurospora also provided an
incentive to continued efforts to probe the basic processes
further with the aid of even simpler organisms. The bacteria are
even more primitive than Neurospora. The bacterial genetic
mechanism was little known; many even doubted that they had one
comparable with that of the higher forms of life. Tatum extended
the approaches worked out in Neurospora to the bacteria.
When Lederberg came to Tatum's laboratory as a young student,
they discovered that different bacterial strains could be crossed
to produce an offspring containing a new combination of genetic
factors. This is the counterpart of the normal sexual
fertilization in higher organism; it is usually considered
preferable here, however, to speak of «genetic
recombination». Bacterial genetics has been developed,
primarily through the efforts of Lederberg and his coworkers,
into an extensive research field in recent years. He also
contributed further evidence that the genetic mechanism of the
bacteria corresponds to that of the higher organisms. Moreover,
thanks to their simple structure and extraordinarily rapid
growth, bacteria provided new and excellent possibilities for a
more profound study of the genetic mechanisms. Lederberg has made
many contributions in this field. Particularly important is his
discovery that sexual fertilization is not the only process
leading to recombination of characters in bacteria. Bits of
genetic material can, if they are introduced into the bacterial
body, become part of the genetic material of the bacterial cell
and thus change its constitution. This is usually termed
«transduction», and it is the first example
demonstrating that it is possible experimentally to manipulate an
organism's genetic material and to introduce new genes into it
and, the organism new characters. Studies in this are now being
carried out in many laboratories in different parts of the
world.
The transduction process and certain other related phenomena have
greatly improved our means of penetrating experimentally into the
basic processes of cell function and cell growth. In all
probability they will also prove to have great significance in
the study of the function of the higher organisms under normal
and pathologic conditions. Work in this field, carried out in
laboratories throughout the world, has already greatly expanded
our knowledge of the basic processes in bacteriophage infection
and of the mechanism of virus infection. The observations also
have opened the way to a more profound understanding of certain
growth problems. Certainly cancer research will be increasingly
influenced by the evolution of our knowledge of the organization
of the genetic material and its manner of functioning, that has
been made possible by the discoveries of this year's three
winners of the Nobel Prize in Physiology or Medicine.
Doctor Beadle and Doctor Tatum. In consequence of an exemplary collaboration in which each has complemented the other to unusual advantage, it has been given to you to make discoveries of fundamental importance to our understanding of the mechanism of Life's processes.
Doctor Lederberg. At first in collaboration with your co-winners of this year's Nobel Prize, and subsequently, along ever-broadening independent lines, you have made possible the advance of research to the structure of the actual genetic material.
Gentlemen. In recognition of your
outstanding contributions to science the Karolinska Institute has
awarded you this year's Nobel Prize in Physiology or Medicine. On
behalf of the Institute I wish to extend the warmest
congratulations from your colleagues on your brilliant
achievements.
It is my honoured privilege now to invite you to receive your
awards from the hands of His Majesty the King.
From Nobel Lectures, Physiology or Medicine 1942-1962, Elsevier Publishing Company, Amsterdam, 1964
Copyright © The Nobel Foundation 1958