Fossett N G, Byrne B J, Kelley S J, Tucker A B, Arbour-Reily P, Lee W R
Louisiana State University, Institute for Mutagenesis, Baton Rouge 70803-1725.
Mutat Res. 1994 May 1;307(1):213-22. doi: 10.1016/0027-5107(94)90294-1.
Tritium beta radiation (3H beta-radiation) in the form of tritiated water was used to induce mutations at the alcohol dehydrogenase (Adh) locus in male Drosophila melanogaster post-meiotic germ cells. All 23 Adh null mutations were large deletions (> 20 kb), determined by genetic complementation and Southern blot analyses. 27 Adh null mutations have been induced by 100-kVp X-rays (Aaron, 1979) and have been genetically and molecularly characterized (Ashburner et al., 1982; Chia et al., 1985; LoMonaco et al., 1987; Mahmoud et al., 1991). In contrast to 3H beta-radiation, 100-kVp X-rays induced a bimodal distribution of Adh null mutations, intragenic mutations, < or = 250 bp, and large deletions, > 100 kb. A statistically significant difference was observed between the frequency of large deletions (23/23 or 1.0) induced by 3H beta-radiation and the frequency of large deletions (19/27 or 0.7) induced by 100-kVp X-rays. However, a statistical difference was not observed between the size distribution of the large deletions induced by 3H beta-radiation and X-rays. The relative deletion frequency (RDF) induced by 3H beta-radiation and 100-kVp X-rays was (1.0/0.7 = 1.4). The relative biological effectiveness (RBE) of these two radiation sources was 1.4, determined from the ratio of the regression coefficients of the respective 3H beta-radiation and X-ray sex-linked recessive lethal (SLRL) dose-response data. The large difference in size between the two classes of X-ray-induced Adh null mutations and the increase in mutation frequency and deletion frequency for 3H beta-radiation with respect to X-rays may indicate that the relative deletion frequency (RDF) is the molecular biological basis for the increase in the RBE for radiation sources with a mean LET value < or = 10 keV/microns.
以氚化水形式存在的氚β辐射（³Hβ辐射）被用于诱导雄性黑腹果蝇减数分裂后生殖细胞中乙醇脱氢酶（Adh）基因座的突变。通过遗传互补和Southern印迹分析确定，所有23个Adh无效突变均为大缺失（>20 kb）。100 kVp的X射线已诱导出27个Adh无效突变（Aaron，1979年），并且已对其进行了遗传和分子特征分析（Ashburner等人，1982年；Chia等人，1985年；LoMonaco等人，1987年；Mahmoud等人，1991年）。与³Hβ辐射相反，100 kVp的X射线诱导出Adh无效突变、基因内突变（≤250 bp）和大缺失（>100 kb）的双峰分布。在³Hβ辐射诱导的大缺失频率（23/23或1.0）与100 kVp的X射线诱导的大缺失频率（19/27或0.7）之间观察到统计学上的显著差异。然而，在³Hβ辐射和X射线诱导的大缺失的大小分布之间未观察到统计学差异。³Hβ辐射和100 kVp的X射线诱导的相对缺失频率（RDF）为（1.0/0.7 = 1.4）。根据各自的³Hβ辐射和X射线性连锁隐性致死（SLRL）剂量反应数据的回归系数之比，确定这两种辐射源的相对生物效能（RBE）为1.4。两类X射线诱导的Adh无效突变在大小上的巨大差异以及³Hβ辐射相对于X射线在突变频率和缺失频率上的增加可能表明，相对缺失频率（RDF）是平均传能线密度（LET）值≤1 keV/μm的辐射源RBE增加的分子生物学基础。
