Induction of change in the fungus chaetomium by irradiation with monochromatic ultra-violet and the mechanism of the reaction

1. Change induced in the fungus Chaetomium by irradiation of the spore with monochromatic ultra-violet has been investigated from a quantitative viewpoint. 2. The methods used in irradiation and growth of the material and the measurement of irradiation dose are described. Samples of spores were irradiated monochromatically at 265, 313 and 334 mu. Colonies of single spore origin were obtained by single-spore and dilution plating and each grown in single petrie dishes. 3. Variation was induced by irradiation in the short, middle and long ultra-violet, and included genetic effects, lethal effects and \growth-damage. The nature of variation is discussed. 4. The relative quantities of the genetic effects and \"growth damage\" differed at each wavelength the short ultra-violet being much more effective in inducing \"growth-damage' than genetic effects and the long wavelengths less effective. The lethal effects are shown to involve genetic change. 5. Evidence is presented associating the genetic effects with qualitative gene change which is considered to involve reaction by the protein component of nucleoprotein. b. \"Growth-damage\" is considered to involve an effect upon nucleic acid whereby the normal functioning of the nucleus is prevented resulting in aberrant cell growth. 7. Nucleoprotein is visualised as providing the mechanism of heredity the protein component being concerned with qualitative gene action and nucleic acid with the reproduction of the genetic protein protein and nucleic acid react independently."