Chemical Breakage of Chromosomes

Abstract

IN a paper under the above title, Darlington and Koller¹ have analysed the close similarity between chemical and radiation-induced breakage of chromosomes, and have rejected the physical ‘target' theory of the X-ray phenomenon as propounded by the late Dr. D. E. Lea². First, they criticize the data on which this theory was based, asserting that "temperature control has been largely dispensed with in the experiments used by Lea as evidence"; and secondly, they conclude that "it is scarcely possible to doubt that both X-rays . . . and chemical breakage are immediately determined by chemical processes which in the X-ray case intervene between an ionization and breakage". In fairness to Lea, we feel that we should point out that neither of these statements is a valid criticism of the target theory. The effects of temperature on radiation-induced breakages have been taken into consideration, and it has been almost axiomatic among physicists that chemical processes follow on the initial act of ionization.