XX century, there were several important discoveries and inventions underlying genetic engineering. After many years of trying to "read" that biological information that is "written" in the genes. This work was started by the English scientist F. Sanger and the American scientist William Gilbert (Nobel Prize in Chemistry in 1980). As is known, the genes contain information instruction for the synthesis of RNA molecules in the body, and proteins, including enzymes. To make the cell to synthesize new, unusual for her substance, it is necessary that it synthesized the corresponding sets of enzymes. And for this, or purposefully change the genes contained in it, or to enter into it new, of missing genes. Changes of genes in living cells - this mutation. They are under the influence of, for example, mutagens - chemical poisons or radiation.
Frederick Sanger
Walter Gilbert