IN 1973 scientists integrated a number of esoteric techniques in microbial and molecular biology, making possible the directed molecular recombination of DNA. By this method, fragments of DNA from any source could be spliced in the test tube and cloned in host organisms. Scientists soon devised other ingenious techniques for manipulating DNA, including improved methods for isolating genes and determining their sequences. These developments have had a major impact on research in virtually every branch of the biomedical sciences. They have also created a burgeoning biotechnology industry that encompasses medicine, agriculture, and pollution control.