Many scientists are worried about mankind's genetic pollution by defective genes which escape the net of natural selection. Some biologists, however, are encouraged by recent progress in genetics, and a few are even emboldened to think imaginatively about control of heredity. In fact, so imaginative is their thinking that their symposium1 on the Control of Human Heredity and Evolution could pass for science fiction, particularly in the section which deals with directed gene-mutation.
Otherwise known as "genetic surgery" or "genetic engineering," directed mutation could be attained by methods—most of them in the conjectural stage —involving complex transfers between gene constituents of a nuclear chromosome and those of an introduced synthetic or natural homologue. Conceivably, a synthetic gene component complementary to a defective counterpart in the chromosome could be pretreated so as to carry a chemical group capable of correcting the defect by mutation. It could then be introduced into