ABSTRACT
Drosophila eggs at nuclear multiplication or blastoderm stages were regionally irradiated with monochromatic u.v. Twenty-four hours after irradiation, the results were classified as normal larvae, undifferentiated eggs, or defective embryos; the latter were subdivided into embryos with anterior or posterior defects, or embryos without anterior and posterior specificity. The irradiation of anterior (posterior) egg regions and the occurrence of anterior (posterior) defects were strongly correlated. These correlations were found using eggs of both stages. The size of the irradiated area did not obviously influence the types of defect.
Dose-response curves were established irradiating anterior quarters of eggs at 245, 265, 285, or 305 nm wavelength. The frequency of embryonic defects increased with increasing u.v. doses, whereas the dosages applied did not increase the frequency of undifferentiated eggs over the control level. In eggs during nuclear multiplication 285 nm radiation was most effective in producing embryonic defects. After blastoderm formation, the efficiency of irradiation was generally increased but similar at all wavelengths employed. The induction of embryonic defects was photoreversible after u.v.-irradiation at the blastoderm stage. The data reported also include transmittance spectra of chorion and egg membrane preparations from Droso-phila eggs.
