A genetic and cytological investigation of the effects of ethyl methanesulfonate on plants
Koehler, Donna Isabel Kinnie
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The induction of mutations by the use of chemicals is still a relatively new field of research. Since 1946, when the first published reports on effective chemical mutagens appeared, many workers have tested a variety of chemical compounds for their ability to produce mutations. Until very recently no chemical mutagens had been found which equalled or surpassed ionizing radiation in the production of genetic changes. However in 1959 Heslot et al., treated barley with a considerable series of related organic compounds and found one, ethyl methanesulfonate, that induced chlorophyll mutations at a much higher rate than did even the largest tolerated doses of radiation. The results are extremely important since with high chlorophyll mutation rates the chances of obtaining desirable mutations are presumed to be correspondingly increased. This is only a presumption since there is a possibility that a mutagen might alter certain genes only, or might cause chromosome breaks only in specific (e.g. heterochromatic) regions (McLeish, 1953). Some chemicals (Ehrenberg, Gustafsson & Lundqvist. 1958) have been found to induce a relatively low proportion of chromosome aberrations and still produce a high mutation rate. From the genetic standpoint, this is of advantage since fewer chromosome aberrations would in turn lead to less disruption of the division mechanism. Mutations produced would be tentatively attributed to true 'point' or gene mutations. It was considered of interest to discover whether or not EMS is a chemical which causes effects of this sort. Since EMS is the most potent of the plant mutagens described up to the present, a detailed investigation of its effects on plants was undertaken.