Recombinant DNA (rDNA) technology is the technique of manipulating the genome of a cell or organism to change the phenotype desirably. The basic steps involved in the process are: 1. Isolating genomic DNA or a donor. The cell or organism from which the required gene is taken is called donor. 2. Fragmenting this DNA using molecular scissors (Enzymes Restriction Endonuclease). 3. Screening the fragments for the desired gene. 4. Inserting the fragments with the desired gene into a cloning vector (plasmid, cosmid or phage DNA) to develop a recombinant DNA or chimeric DNA. 5. Introducing the recombinant vector into a competent host cell. 6. Culturing these cells to obtain multiple copies or clones of the desired fragment of DNA. 7. Using these copies to Transform suitable host cells so as to express the desired gene. Examples of the therapeutic products produced by r-DNA technology are: 1. Blood proteins: Erythropoietin 2. Human Hormones: Insulin, 3. Immune modulators : $$alpha$$-Interferon, $$eta$$ interferon, 4. Vaccines: Hepatitis B.