Mutagenesis by ultraviolet and visible light. I: Early work on macro-organisms

Abstract

Research on the mutagenic action of UV started very soon after the discovery of X-ray mutagenesis. By the early thirties, it had been established that UV can produce mutations in Drosophila and flowering plants. Research was carried on with three principal aims in mind. One concerned the relationship between intragenic mutations and intergenic structural changes, which was then a very much debated topic. The X-ray data allowed no decision as to whether the two types of event have the same cause. Indeed, as mentioned in Chapter 6, some geneticists believed that all X-ray induced mutations were in reality chromosome rearrangements. Since UV, in contrast to X-rays and other high-energy radiation, produces only atomic excitations but no ionizations, the question could be asked whether perhaps structural changes required ionization for their production. The answer, as we shall see presently, was negative. All the same, the proportion of rearrangements among UV-induced mutations was generally low, and this led to the second aim, which was to analyse the nature of gene mutations by means of an agent that is less destructive than X-rays. This approach was to bear full fruit later, when the chemical nature of the genetic material had been elucidated.