Article: Recombinant DNA

Recombinant DNA (sometimes rDNA) is an artificial DNA sequence resulting from the combining of two other DNA sequences in a plasmid. Recombinant proteins are proteins that are produced by different genetically modified organisms following insertion of the relevant DNA into their genome. As this recombines the DNA of two different organisms, the word recombinant is used to refer to this process. Recombinant DNA technique was discovered by Stanley Cohen and Herbert Boyer in 1973, Nov 1973 publication of “Construction of Biologically Functional Bacterial Plasmids in vitro”, this paper described a technique to isolate and amplify genes, or DNA segments, and insert them into another cell with precision. Recombinant DNA technology was made possible by the discovery of restriction endonucleases by Werner Arber, Daniel Nathans, and Hamilton Smith, for which they received the 1978 Nobel Prize in Medicine.

The term recombinant DNA refers to a new combination of DNA molecules that are not found together naturally. Although processes such as crossing over technically produce recombinant DNA, the term is generally reserved for DNA produced by joining molecules derived from different biological sources.

Uses

Recombinant DNA is used for genetic transformation to produce genetically modified organisms. Some examples of recombinant DNA products are peptide hormone medications including insulin, growth hormone, and oxytocin. Vaccines can also be produced using recombinant processes. The organism most commonly used is Escherichia coli.

Plasmids and recombinant DNA technology

Plasmids are extranuclear fragments of DNA present in some bacteria. A plasmid can transfer genetic material to another bacterium, allowing it to express the transmitted gene(s). Restriction enzymes which cut sequences of DNA at certain spots are used to splice into a plasmid the DNA sequence for the desired gene. The plasmid is then inserted into a bacterium in order to express the gene and produce the protein coded for by the gene. Large amounts of the protein can be produced in a factory with vats of the genetically engineered bacteria.

Eukaryotes cannot use circular DNA such as that present in a plasmid. Other systems, such as transfection with viruses, are used instead.

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