Manipulation of DNA in genetic engineering became possible due to the discovery of:

Genetic engineering, also called recombinant DNA technology, involves the group of techniques used to cut up (by restriction enzymes) and join together (via DNA ligase) genetic material, especially DNA from different biological species, and to introduce the resulting hybrid DNA into an organism in order to form new combinations of heritable genetic material. Related Theory Restriction endonucleases cut DNA molecules at specific places into many smaller fragments called restriction fragments.