[Recombinant DNA studies, a controversial subject which is also promising from the point of view of veterinary medicine (author's transl)].

The hereditary characters of organisms are bound up in the DNA of their genomes. Genetic information is expressed by a complicated mechanism. The process by which this occurs and the control of the degree of expression in bacteria and a number of the other lower organisms are known only in broad outline. There usually is no exchange of DNA between organisms of unrelated species in nature. "Foreign" DNA can be linked to bacterial plasmid DNA and multiplied in the laboratory as a recombinant DNA molecule in bacteria using the recently discovered so-called restriction enzymes. Expression of bacterial DNA can thus be accomplished in a different, unrelated bacterium. In principle, this means that the natural barriers between unrealated species of organisms may be passed by. Human and animal DNA can also be multiplied in bacteria by this method. Previous recombinant DNA studies showed that the mode of expression of genetic information in the higher organisms differs markedly from that in bacteria. The initially sanguine expectations regarding the practical use of recombinant DNA research, for instance in the production of biologically important substances by bacteria, will therefore possibly not be realized at short notice. On the other hand this technique has added considerably to the knowledge of expression of genes within a short space of time. This is particularly true of the mechanisms of pathogenicity of E. coli, the bacterium which plays such an important role in veterinary medicine. The recombinant DNA technique is briefly reviewed in the present paper. The uses are broadly outlined, and one of these, which could be of importance in veterinary medicine, is described in greater detail. International discussions of potential hazards, and therefore also of the admissibility of this type of experiment, are griefly summarized.