Sequence analysis of 7 spontaneous, 27 γ-ray- and 20 neutron/neutron+γ-ray-induced black (b) point mutants was carried out. All these mutants were isolated as non-mosaic transmissible recessive visibles in the progeny of irradiated males from the wild-type high-inbred laboratory D32 strain of Drosophila melanogaster. Among spontaneous mutants, there were two (28.5 %) mutants with copia insertion in intron 1 and exon 2, three (42.8 %) with replacement of b^+D32 paternal sequence with maternal b¹ sequence (gene conversion), one (14.3 %) with 142-bp-long insertion in exon 2, and one (14.3 %) with a short deletion and two single-base substitutions in exon 3. Among γ-ray-induced mutants, there were 1 (3.7 %) with copia insertion in intron 2, 6 (22.2 %) with gene conversion, and the remaining 20 (74.1 %) mutants had 37 different small-scale DNA changes. There were 20 (54.1 %) single- or double-base substitutions, 7 (18.9 %) frameshifts (indels), 9 (24.3 %) extended deletions or insertions, and 1(2.7 %) mutant with a short insertion instead of a short deletion. Remarkably, clusters of independent small-scale changes inside the gene or within one DNA helical turn were recovered. The spectrum of DNA changes in 20 neutron/ neutron+γ-ray-induced mutants was drastically different from that induced by γ-rays in that 18 (90.0 %) mutants had the b¹sequence. In addition, 2 (10.0 %) with gene conversion had 600- or 19-bp-long deletion in exon 3 and 1 (5.0 %) mutant with a short insertion instead of a short deletion. Analysis of all 27 mutants with gene conversion events shows that 20 (74.1 %) had full b¹ sequence whereas 7 others (25.9 %) contained a partial b¹ sequence. These data are the first experimental evidence for gene conversion in the early stages of animal embryogenesis in the first diploid cleavage nucleus after male and female pronuclei have united. The gene conversion, frameshifts (indels), and deletions between short repeats were considered as products of a relevant DNA repair pathways described in the literature. As the first step, the gametic doubling doses for phenotypic black point mutations and for intragenic base substitution mutations in mature sperm cells irradiated by 40 Gy of γ-rays were estimated as 5.8 and 1.2 Gy, respectively, showing that doubling dose for mutations at the molecular level is about 5 times lower than that at the phenotypic level.

对 7 个自发的、27 个 γ 射线和 20 个中子/中子+γ 射线诱导的黑色 (b)点突变体进行序列分析。所有这些突变体在来自野生型高近交实验室 D32黑腹果蝇株的辐照雄性后代中被分离为非镶嵌可传播隐性可见体。在自发突变体中，有两个 (28.5 %) 突变体在内含子 1 和外显子 2 中插入了copia ，三个 (42.8 %) 用母体b ¹替换了b ^+D32父系序列序列（基因转换），一个（14.3 %）在外显子 2 中插入 142 bp 长，一个（14.3 %）在外显子 3 中有一个短缺失和两个单碱基替换。在 γ 射线诱导的突变体中，有 1 (3.7 %) 有copia插入内含子 2, 6 (22.2 %) 与基因转换，其余 20 (74.1 %) 突变体有 37 种不同的小规模 DNA 变化。有 20 个 (54.1 %) 单碱基或双碱基取代，7 个 (18.9 %) 移码（插入缺失），9 个 (24.3 %) 延伸缺失或插入，以及 1 (2.7 %) 个短插入而不是短插入的突变体删除。值得注意的是，基因内部或一个 DNA 螺旋转角内的独立小规模变化簇被恢复。20个中子/中子+γ射线诱导的突变体的DNA变化谱与γ射线诱导的突变体有很大的不同，其中18个（90.0%）突变体具有b ¹顺序。此外，2 (10.0 %) 具有基因转换的突变体在外显子 3 中有 600 或 19 bp 长的缺失，而 1 (5.0 %) 突变体具有短插入而不是短缺失。对所有 27 个具有基因转换事件的突变体的分析表明，20 个 (74.1 %) 具有完整的b ¹序列，而其他 7 个 (25.9 %) 包含部分b ¹序列。这些数据是动物胚胎发生早期在雄性和雌性原核结合后的第一个二倍体分裂核中基因转换的第一个实验证据。短重复之间的基因转换、移码（插入缺失）和缺失被认为是文献中描述的相关 DNA 修复途径的产物。作为第一步，表型的配子加倍剂量经 40 Gy γ 射线照射的成熟精子细胞中的黑点突变和基因内碱基置换突变估计分别为 5.8 和 1.2 Gy，表明分子水平上的突变加倍剂量比表型水平。