RAUT, CAROLINE, Detroit Institute of Cancer Research, and Wayne Univer-
sity College of Medicine, Detroit, Michigan. The effect of ultraviolet light
of various wavelengths on the production of cytochrome-deficient yeast. --
Normal and cytochrome-deficient haploid strains of yeast were irradiated at
various wavelengths of ultraviolet light. Both strains were killed at com-
parable rates with maximum rate of kill at 2600 4. The action spectrum cor-
responds to the absorption spectrum of nucleic acid, A large proportion of
the survivors of the irradiated normal cells produce cytochrome-deficient
"petite" colonies, This cytochrome deficiency is cytoplasmically rather than
genically determined, The production of petite colonies also exhibits a
maximum at 2600 4, It is suggested that absorption of ultraviolet by nucleic
acid is involved in the destruction or inactivation of the cytoplasmic particles
necessary for the production of the complete cytochrome system and possibly
that the particles themselves contain nucleic acid,