Strain Sensitivity of Silkworm Eggs to Killing and Mutation by Ultraviolet Light

Killing and mutation by ultraviolet light was compared among different x-ray-sensitive silkworm strains. After mature oocytes and eggs at early cleavage stages were irradiated with varying doses of UV, embryonic mortality and mutation frequency at pe:re egg-color-specific loci were measured. Strain differences in UV sensitivity were found for both effects on oocytes as well as on eggs: for killing, the difference between the most resistant and sensitive strains was four to six times, and for mutation induction was seven times. A consistent positive correlation was found between sensitivity to killing and sensitivity to mutation induction. No positive correlation was found between UV and x-ray sensitivities for either biological effect. In treated oocytes, more fractional-body than whole-body mutations were induced by UV, while more whole-body than fractional-body mutations were induced by x-rays.