Murakami A
Radiat Environ Biophys. 1976 Oct 7;13(3):187-95. doi: 10.1007/BF01330763.
The physical induction of recombinational events has been studied in the female silkworm (Bombyx mori), in which crossing-over does not normally occur. Female silkworms heterozygous in the trans type of two egg-color genes, pe (V-0.0) and re (V-31.7), received a single dose of X-rays (1000 R) at various developmental stages. Then they were crossed to marked males homozygous for both genes. The results indicated that X-rays increase the occurrence of recombinational events in silkworm females from first instar larvae to late stage pupae. The spontaneous frequency of exchange type recombinants in the control series was 2.5 X 10(-5), while after irradiation the frequency of these recombinants was up to 38.8 X 10(-5). The sensitive stage to X-ray-induced recombinational events was late stage larvae from fourth to fifth instar. Exchange (cross-over) type recombinants were about three times more frequent than interchange types among the 122 recombinants recovered. The biological significance of the present finding is discussed.
已经在雌蚕（家蚕）中研究了重组事件的物理诱导，在雌蚕中正常情况下不会发生交叉互换。在两个卵色基因（pe，位于V染色体0.0位置；re，位于V染色体31.7位置）的反式杂合雌蚕在不同发育阶段接受单次剂量的X射线（1000伦琴）照射。然后将它们与两个基因均为纯合的标记雄蚕杂交。结果表明，X射线可增加从一龄幼虫到蛹后期雌蚕中重组事件的发生率。对照系列中交换型重组体的自发频率为2.5×10⁻⁵，而照射后这些重组体的频率高达38.8×10⁻⁵。对X射线诱导的重组事件敏感的阶段是四龄到五龄的后期幼虫。在回收的122个重组体中，交换（交叉互换）型重组体的频率大约是互换型的三倍。讨论了本研究结果的生物学意义。
