Loovetefects of Radistion (Dr. bellany) (3) Mutations-—processes by which germinal material changes in such a way that @ new charecter-~-or one not previously knoWre-appears suddenly and is inherited without further change. Or at any rate, without further change until a new mutation occurs rfeeting the same locus or trait. The cause or causes of mutation have long been a puzzle. fron complete and many questions are as yet unanswered. causes of mutation, it should be clear that by in mutation rate. Investigations are far In the discussion of possible causes of mutation we refer always to chan Just as the investigator using a Geiger-Muller counter estimates redioactivity in terms of counts ebove background, so te gensticist measures mutation rE as ge multiple of the base or natural rete, hadiant energy: Tronty-one years eso Muller demonstrated clearly that mutation wate cen be increased by exposing DroSophila banana fly to X-rays. Ultra-violet light w: Sinee 1927, mutation rate changes followins exposure to Xerays, famm rediation acd in « few instances to particle rediation (msinly beta) have been studied in a con- able number of orgenisms ranging through the viruses, bacteria, plants and animals. Increases un to several thousand percsit are not unusual. This is one place, however, « npressing resvlts in percentage may be a little Misieading. “ith a base rate of {0-4 a incvease cf 100% in rate would mean txo mutations in a million; 3000%, 30 in a million. the tric: for the geneticist, is to find those few in a million. There cen be ne reasonable doubt that at lezst one of the causes of mtation i: ionizetion (from radietion) and change in energy levels resulving in a chemical chenge : the genes. saves: ae an Other forms of radiant energy---Ultra-violet light aad very high frequency rad Experimentation with ultra-violet light is complicated by reason of its small penetrating power. Small but significant increases in mtation rates of Drosophila and corn have been demonstrated. Very high frequency electromagnetic fields have not been well investigated. Significant changes in the lethe] mutation rate and other changes huve been demonstrate in Drosophila, however, Hae