The use of radioactive isotopes in the study of life processes is of
importance in understanding them. With the use of autoradiographic and
radiochemical techniques, it is possible to obtain valuable information
regarding the life of cells and the intimate mechanisms by which life
processes determine the fate of the entire organism.
Our knowledge of the cell cycle and of the gene-action system has been
useful in determining how organisms grow and how cancer cells behave. It
has been determined that certain normal adult cells divide more
frequently than some cancer cells and that the growth of cancers depends
not so much on the speed of cellular proliferation as on the number of
cells actually dividing.
[Illustration: Figure 29 _Radioautograph showing DNA synthesis during
chromosome replication. Chromosomes from cells in the root tip of the
Tradescantia plant were labeled with ³H-thymidine. In A and B, the
midportion of DNA synthesis, the radioisotope is distributed throughout
the chromosome arms; in C, near the end of DNA synthesis, it is confined
mainly to the end of the arms._]
Knowledge of the cell cycle has also brought new insight to the control
of cell division, as in studies related to the therapy of cancer. The
most important problem now is, not the control of cell division, but the
control of the synthesis of DNA.
Our information on the gene-action system provides broad new opportunity
for the investigation of many life processes. Hormone action, processes
by which the body develops immunity to disease, and even cell division
itself are apparently regulated through the gene-action system. This, in
turn, offers possibilities for investigations meant to control these
processes.
It is difficult to chart the future course of modern molecular biology,
but it is not difficult to predict that the next few years will bring to
biology the same kind of sweeping advances that revolutionized physics a
few decades ago. The DNA molecule has been called the atom of life. When
we have harnessed it, the harnessing of the uranium atom will seem, in
comparison, a result of scientific adolescence. When man has mastered
the genetic code, he’ll hold a vast power in his hands—power over the
nature of coming generations.