Graf U
Institute of Toxicology, Swiss Federal Institute of Technology (ETH), Schwerzenbach.
Experientia. 1995 Feb 15;51(2):168-73. doi: 10.1007/BF01929364.
The relationship between the induction of mutant clones and the time of mutagen treatment was studied in the somatic mutation and recombination test (SMART) in wing cells of Drosophila melanogaster. Larvae trans-heterozygous for the recessive marker mutations multiple wing hairs (mwh) and flare (flr) were produced. Batches of these larvae were then treated with mutagen at different ages spanning all three larval instars. Methyl methanesulfonate was fed acutely for 2 h by immersing the larvae in a solution of the mutagen mixed with powdered cellulose. Wings of the surviving adult flies were mounted and scored for the presence of spots. The frequency and size of single and twin spots were recorded separately. Twin spots are produced exclusively by mitotic recombination, whereas single spots can result from various types of mutational and exchange events. There exists a clear correlation between time of induction and frequency as well as size of the single spots. In young larvae only few but very large spots are induced, whereas in older larvae the frequencies are considerably increased but the sizes are smaller. The twin spots show a different relationship. Practically no twin spots are found in very young and in very old larvae. The results demonstrate that in the wing spot test the optimal age of the larvae for mutagen treatment is 72 h.
在果蝇翅细胞的体细胞突变和重组试验（SMART）中，研究了突变克隆的诱导与诱变处理时间之间的关系。产生了对隐性标记突变多翅毛（mwh）和耀斑（flr）呈反式杂合的幼虫。然后，在涵盖所有三个幼虫龄期的不同年龄阶段，对这些幼虫批次进行诱变处理。通过将幼虫浸入与粉状纤维素混合的诱变剂溶液中，急性喂食甲磺酸甲酯2小时。将存活成虫的翅膀固定并对斑点的存在情况进行评分。分别记录单斑点和双斑点的频率和大小。双斑点仅由有丝分裂重组产生，而单斑点可由各种类型的突变和交换事件导致。诱导时间与单斑点的频率和大小之间存在明显的相关性。在幼虫早期，仅诱导出少数但非常大的斑点，而在老龄幼虫中，频率显著增加但斑点较小。双斑点呈现出不同的关系。在非常年幼和非常老龄的幼虫中几乎没有发现双斑点。结果表明，在翅斑试验中，幼虫进行诱变处理的最佳年龄为72小时。
