Genes & Mental Defectives

Is mental deficiency genetically determined? Probably so, says California Institute of Technology's famed Chemist Linus Pauling. Last week the Ford Foundation announced that it was betting $450,000 (to be spread over five years) on Pauling's hunch.

In all the world, no man was better fitted than Nobel Prizewinner Pauling to probe this problem. In 1949 he crashed through the barrier separating chemistry from medicine when he headed a team of researchers who pinpointed the cause of sickle-cell anemia. Medical men had long known that this disease, common among African peoples (and their U.S. descendants), was inherited in some fashion, but that was all they knew. Pauling showed that the abnormal, short-lived, sickle-shaped red blood cells, characteristic of the disease, contained Hemoglobin S, a hitherto unknown form of hemoglobin that differs in molecular structure from the normal Hemoglobin A. More important, Pauling & Co. showed that a defective gene determined the production of this type of hemoglobin. If both parents had the defective gene, even without the overt disease, the chances that their offspring would have full-fledged anemia were (by Mendelian law) one in four.

Now Pauling believes that mental deficiency may be similarly caused by defective molecules. Of all mental char acteristics, intelligence is the one most easily measured and least subject to change. Studies have shown that the children of the intelligent are more likely to be intelligent than those of the unintelligent. Pauling would like to carry this proposition several steps farther. "We believe," he says, "that significant progress can be made in the attack on mental deficiency by ... fundamental research employing the most powerful techniques of modern chemistry ... to understand the causes and workings of certain abnormal molecules."

Pauling's argument: molecular disease arises when defective genes cause the body to manufacture abnormal molecules. Up to i% of the 2,000,000 mental defectives in the U.S. suffer from phenylketo-nuria--a mental disease accompanied by the body's failure to oxidize an amino acid, phenylalanine, to tyrosine. Probable cause of the failure is a defective enzyme. The Pauling project: to find out the connection between the molecular and men tal defects, and also whether the other 99% or more of mental defectives owe their handicap to a similar molecular abnormality caused by a combination of defective genes in their parents.

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