Plasmid

Plasmid is Part of Bacteria

Plasmids are small, circular molecules of double stranded deoxyribonucleic acid (DNA) that exist in the cytoplasm of many bacteria. Plasmids carry genes for several different properties, including resistance to various drugs and chemicals, as well as the ability to synthesize toxins that adversely affect foreign species of bacteria. In some cases, plasmids can be rapidly transfer to cell to cell by means of hair-like structure, called sex pilli, that project from the cell surface. Cell to cell plasmid transfer can result in various properties carried on a transmissible plasmid being rapidly disseminated throughout an entire population of bacteria. This property has been responsible fro the appearance of various bacterial populations that are resistant to common antibiotics.

Recently, research involving plasmids has been directed toward gene splicing techniques in the field of genetic engineering. Plasmid DNA is isolated from bacteria, and its circular structure is broken by specific enzymes. A foreign DNA segment is then inserted in the plasmid, and the circle is resealed by other enzymes. A foreign DNA segment is then inserted in the plasmid, and the circle is resealed by other enzymes. This reconstructed plasmid, which contains an extra gene, can be replaced in the bacterial cell. Under the proper conditions the cell will synthesize the product of the foreign gene as well as those codec by its own DNA.

Those technique use on DNA engineering on how modification a gene from specific source, may come from bacteria or viruses or from plant, then create a new cell that can be use to destroy cancer cell for example. The technique to cut this DNA is use certain enzyme. This enzyme also can directly use for cancer drug that can directly to destroy a cancer cell through DNA information code that always reproduce by themselves. The reproduction of cancer cell can be stop by cut the right information DNA.