recombinant DNA - Uses, Plasmids and recombinant DNA technology

Hybrid (recombinant) nucleic acid molecules generated by genetic engineering technology through the use of restriction enzymes (present in many micro-organisms) that can cut double-stranded DNA molecules at a specific sequence, usually 4–8 base pairs. Each enzyme recognizes a different base sequence. DNA fragments produced by the cleavage with a particular restriction enzyme can be joined and the joint resealed through the use of an enzyme called DNA ligase, so that the molecules composed of the DNA segments from unrelated organisms may be artificially recombined to produce genes which do not occur in nature. The resulting recombinant genes are initially propagated in bacteria (or sometimes yeast) as part of independent circular DNA molecules known as plasmids. This technology is at the basis of numerous applications, including research into gene structure and function, screening for the presence of a particular disease gene (eg Huntington's chorea, cystic fibrosis, haemophilia), somatic gene therapy, and the generation of genetically modified organisms.

Recombinant DNA (sometimes rDNA) is an artificial DNA sequence resulting from the combining of two other DNA sequences in a plasmid. A recombinant protein is a protein produced by an organism after the relevant DNA is inserted into its genome (that is, by a genetically modified organism).

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.

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.

Plasmids and recombinant DNA technology

Plasmids are extranuclear fragments of DNA present in some bacteria. Restriction enzymes which cut sequences of DNA at certain spots are used to splice into a plasmid the DNA sequence for the desired gene.

Most eukaryotes cannot use circular DNA such as that present in a plasmid.