The chemical production of mutations. The effect of chemical mutagens on cells and their genetic material is discussed.

Since the discovery of the first potent mutagens over 20 years ago, progress in mutation research has been rapid. Many new mutagens, belonging to a variety of chemical classes, have been discovered, and for some of them the reaction with DNA in vitro has been established. It seems that the findings of these chemical investigations usually also apply to viruses which are treated outside the cell. This has made chemical mutagens into an important tool for the analysis of the genetic code. When DNA is treated inside the cell, its reactions would not be expected to be always identical with those observed in vitro; in one case they have, indeed, been found to be different.