Recombinant DNA and genetic techniques. Recombinant DNA (or rDNA) is made by combining DNA from two or more sources. In practice, the process often involves combining the DNA of different organisms.The process depends on the ability to cut and re-join DNA molecules at points which are identified by specific sequences of nucleotide bases called restriction sites.n practice, the process often involves combining the DNA of different organisms. The process depends on the ability to cut and re-join DNA molecules at points which are identified by specific sequences of nucleotide bases called restriction sites.