Abstract
Dose response relationship of the X-ray induced loss of heterozygosity (LOH) was examined in somatic cells of fruit fly Drosophila melanogaster. Using the wing spot test, the frequency of somatic mutation that induced LOH in two external marker genes (mwh and flr, both on the third chromosome) was measured in a post replication repair deficient mutant, mei-41 (a Drosophila homologue of the human ATM gene). In mei-41 heterozygotes in which the repair function is still active, the frequency of mutant spot in the high-dose groups (2 or 3Gy) was higher than that in the sham-exposed group, whereas that in low-dose groups (0.2 or 0.5Gy) was significantly lower than that in the sham-exposed group. There was a threshold at around 1Gy in the dose-response relationship in mei-41 heterozygotes, while in homozygous mei-41 siblings without repair function, the threshold was smaller, and the inclination of the dose-response curve was steeper than in heterozygotes. It is inferred that the DNA repair function is involved in the existence of the threshold. [J Radiat Res 44:402 (2003)]
