Development And Use Of Genetic Engineering

A better understanding of the gene and its action has led scientists to develop techniques that allow them to alter the structure of DNA. Altering the structure of one DNA molecule by substituting genes from another DNA molecule is called genetic engineering. The DNA molecule that is formed by combining two different DNA molecules is called recombinant DNA.
Scientists use the bacterium Escherichia coli to study recombinant DNA. AND. Coli has a large chromosome that is in the cytoplasm. The bacteria can also contain plasmids, which are small circular pieces of DNA. The chromosome and plasmids are duplicated each time the cell divides. Genetic engineers can introduce genes into a plasmid to alter chemical reactions within the cell. So the DNA of this plasmid is broken, at a certain point, by a special kind of enzyme. At the same time that the plasmid is broken, a piece of another DNA molecule breaks in the same way. This piece of DNA is then introduced into the plasmid. The split plasmid binds to the new piece of DNA and returns to the original circular structure. This technique is called DNA splicing. The new plasmid is a combination of the original DNA molecule and a new piece of DNA. This plasmid is reintroduced into the bacteria. When the bacteria duplicates, the new DNA also duplicates. In this way, for example, the insulin gene can be introduced into a bacterial plasmid so that the bacteria synthesize the insulin protein.