Science Notes D.N.A.—Chemical That Holds Secret Of Life

Press, Volume XCIX, Issue 29250, 7 July 1960, Page 19

Science Notes D.N.A.—Chemical That Holds Secret Of Life

[Bl/

RITCHIE CALDER]

Mr Kwame Adjaye, of Accra, Ghana, asks: “What exactly is D.N.A.? I have seen it referred to several times as ‘the chemical which holds the secret of life’. Is this true?”

Answer: No less. If, without going into a philosophic argument on “What is life?”, we accept a limited scientific definition that a thing “lives” if it reproduces itself (like the cells of the body and the species of plants, animals and humans) then this is it.

D.N.A., that is to say Deoxy-ribonucleic-acid, is a chemical which not only reproduces itself but provides the chemical mechanism by which the most complex living structures reproduce themselves. With R.NA. (Ribonucleicacid) it is a basic chemical of the living cell. The chemists had long known the constituents of D.N.A.—sugars, phosphates, and four different substances containing nitrogen. But that gave no clue to its biological action. They did not know how these constituents were arranged, nor in what way they influenced the living processes. Then Watson and Crick, at the Cavendish Laboratory, Cambridge, suggested that the molecule of D.N.A. was a “double helical chain,’* like the twist of electrical flex. The physicists went even further, and with X-rays showed how the various atoms of the lonstituents were arranged along his flex. They found that the nitrogen-containing chemicals were always disposed in certain orders ana upon the particular order depended a whole lot of things. i In fact the order was a chemical code which transmitted “instructions’* from one generation to another. And by “generation** is meant not only from parent to child, but from cell to cell in the constantly renewing processes of the body. Thus the D.N.A. of a kidney cell would always reproduce another kidney cell, and so with the brain cell, and with the skin cell, etc. So tod, the germ-cells carrying an immense number of instructions would, chemically, transmit hereditary characteristics which would determine the colour of the eyes, the shape of the nose the curl of the hair, or anaptitude for music. If, in these transmitted patterns the position of one of these nitrogen compounds got displaced and another was submitted for it, the characteristics would be changed but the new pattern would go on reproducing itself. This is what scientists call a "mutation.”

Using natural D.N.A., biologists have been able to demonstrate this hereditary process. For example, Professor Jacques Benoit and his colleagues in Paris took the D.N.A., from the cells of one type of duck called Khaki and injected it into young ducks of another strain, Peking. The result was that, even in a duck already born, the characteristics were changed. The Peking ducks were no longer completely Peking, but they were not Khaki either: an entirely' new strain had been created.

The properties of D.NA are still not properly known, but recently an important step was made in that direction when three French research workers, Messrs Polonsky, Douzou and Sadron, described the peculiar electronic properties they had discovered in certain elements of living matter.

Back in 1956, Polonsky had suggested that the cells might be arranged according to an elctronic type pattern. And early this year, Pierre Douzon and Charles Sadron, head of the Macromolecular Research Centre in Strasbourg, provided some basis for. this theory by demonstrating that DHA is endowed with a “memory** and with a capacity for converting energy and for transmitting “information.** If other experiments confirm these properties of D.N.A, important new fields of study will be opened to biological research. Up to now, scientists have been unable to explain why the constituents of the cells are arranged in a given order, still less how D.N.A. exercises a sort of "remote control,” for example, in transmitting genetic “instructions,” or in directing the fundamental life processes.

Life Process . MT P. van der Haegen,'at the University Sanitarium, of Eupen, Belgium, has various questions about the life process: *1 should like to know what the present state of research is regarding the reproduction or creation o an elementary human being?”

Answer: We are a very, very, long way from producing testtube babies. Scientists using radioactive tracers have convincingly demonstrated how plants convert the sun’s rays and the elements of the atmosphere and of the soil into carbohydrates, the sugar and starches necessary as the energy-foods of the life-process. They have an inkling of how plants go on to produce proteins, necessary for the building and maintenanea of tissues. They know that there are 20 or more animo-acids, the chemical I groups or “bricks,” which build

up the structure of protein. They can make most of them synthetically from elements in the laboratory. But they still have not shown convincingly how these bricks can be artificially compounded into proteins. Oh, yes, hey have “made” proteins by feeding them With the chemicals on which they grow, just as they have made organs grow—when they had the natural cells of the organs with which to start.

They know the nature of D.N.A. and R.N.A. which are the active “architect’s blueprints” by which the elements are compounded into cells and tissues and, in principle, into micro-, plant, animal, or human, -organisms. But that is still a long way from sitting down, planning and producing any organism, without the help of nature.

Mr van der Haegen also asks: “Have the scientists succeeded in synthesising protein similar to viruses?”

Answer: No. They have not yet reproduced the simplest cell, or the virus, or the bacterium. They have changed the cell, the virus, the bacterium and even ducks by artificial use of D.N.A. But the D.N.A. was not artificial, in tile sense that it was compounded in the test-tube from original elements. In the case of ducks, it was a matter of isolating D.N.A.

from the cell of one type of duck and injecting it into a duck of another type, whose characteristics were changed. He also asks: “Have any of the Nobel prizewinners for Physiology done research work in this field?”

Answer: Yes. Very notable research work. Kornberg, of the United States, succeeded in growing D.N.A. out of a chemical medium, but he had to use natural D.N.A. as the “primer.” By giving it the elements which he kiiew it needed, he made it grow. In other words, he made a chemical reproduce itself from other chemicals in a test-tube. Thus, he made an elementary form of life. Since then claims have been made that D.N.A. has been grown from a chemical medium, without a “primer.” There is no theoretical reason why this should not be done. It will be. And man will have fabricated the pattern of the living process. But not dramatically—like producing a mannikin in a flask. The structure of a protein such as insulin is know. It can be modified and improved for the benefit of sufferers from diabetes but it has not been built “brick” by "brick.” Viruses have been produced in the form of crystals—inert. Those crystals in .contact with a living substance come alive. Viruses are proteins plus D.N.A., or R.N.A.—the simplest form of the living process, yet still too complicated to make.

The important thing is not that the chemists should create a being a Frankenstein but that, in all this kind of study, scientists are learning about the nature of the cells. And, in that growing knowledge, will be found the answer to problems like cancer —cells which have run amuck. Ultimately, by changing the process of heredity, man might produce a superman—or a monster. But better that we seek to control and avoid hereditary diseases, which, to the scientists, are forms of transmitted protein, modified by D.N.A. (U.NJE.S.C.)