DNA sequencing and recombinant DNA technology in a nutshell

DNA, deoxyribonucleic acid, is genetic material that "encodes" hereditary information by the sequence of four bases: A, T, C, G. Some viruses have a DNA genome, while others (like retroviruses) have an RNA genome which also consists of four bases: A, U (an equivalent to T), C, G. These bases are cyclic molecules that are linked together via a sugar called ribose (in R-NA) or deoxyribose (in D-NA) and phosphate.

The ability to identify specific sequences of these bases opened up a new era in studying gene function and regulation. Typically, a specific DNA sequence contains information for building a sequence of amino acids which are joined together to form a protein. Employing recombinant DNA technology, a known DNA sequence can be transferred into a bacterial cell via so-called "vectors." In vitro designed vectors containing a predetermined sequence facilitate the introduction of genes into a cell and enable us to observe their effects. "Plasmids" - ring-shaped DNA molecules that bacteria may contain as additional genetic material - are frequently used as vectors. With each cell division, plasmids may also replicate and can thus be very efficiently amplified. After numerous cell divisions, the plasmids can be isolated, and the gene of interest can be cleaved out, modified, and used for further studies. Viruses carrying your gene of interest can also be used as vectors by allowing them to infect, for example, a human cell line.

Since bacterial growth not only amplifies the DNA but also increases the production of the protein encoded by that DNA, recombinant DNA technology can be used not only to study gene function but also to produce, for example, vaccines. Another intriguing approach using recombinant DNA technology is "gene therapy," which seeks to selectively introduce DNA into cells or organisms to overcome a gene defect. This therapeutic approach is still in early stages due to the risk of inducing tumors and unwanted immune responses.