Mutation frequency reduction and transcripts variation of the defense response genes by the low dose irradiation in Drosophila

Abstract

We have previously reported that irradiation of the Drosophila immature sperms using gamma rays of 500 µGy from the ⁶⁰Co in one and half minutes reduced the frequency of the sex-linked recessive lethal mutation up to 0.1% (P<0.01) compared with 0.3% in control. It is said that in this level irradiation rarely makes the DNA double strand break and the double strand break repair does not work. To elucidate this phenomenon, we examined the greatest dose that the mutation rate returned to the spontaneous mutation level. We found that the gamma ray irradiation of 40 µGy in one and half minutes raised the sex-linked recessive mutation to the 0.29%. This result was significantly higher than that at 500 µGy (P<0.01) and no difference to that in control significantly (P=0.86). Furthermore, we will report about the expression of the defense response genes and apoptosis genes which were changed the expression levels at the 500 µGy gamma ray irradiation.