Shukla P T, Sankaranarayanan K, Sobels F H
Mutat Res. 1979 Jul;61(2):229-48. doi: 10.1016/0027-5107(79)90130-1.
The X-ray induction of recessive visible specific locus mutations at 14 X-chromsome loci was studied in Drosophila melanogaster using the "Maxy" technique. The X-ray exposure was 3000 R to 5-day-old males and the sampling of germ cells was restricted to mature spermatozoa. Presumptive mutant females recovered in the F1 generation were tested for transmission, allelism, fertility and viability in males. A total of 128 mutations (115 completes and 13 mosaics including those that were male viable as well as male-lethal) recovered among 38 898 female progeny were found to be transmitted. On the basis of the above frequency, the average mutation rate can be estimated as 7.8 X 10(-8)/locus/R; for mutations that were viable and fertile in males, the rate is 3.0 X 10(-5)/locus/R (49 mutations among 38 898 progeny). The frequency of mutations at the different loci encompassed a wide range: while no mutations were recovered at the raspberry and carnation loci, at others, the numbers ranged from 1 at echinus to 31 at garnet; in addition, the proportion of mutations that was male-viable was also different, depending on the locus. Schalet's extensive data on spontaneous mutations at 13 (of the 14 loci employed in the present study) loci permit an estimate of the spontaneous rate which is 6.1 X 10(-6)/locus (a total of39 mutations among 490 000 progeny); for mutations that were viable and fertile in males, the rate is 3.0 X 10(-6)/locus (19 mutations among 490 000 progeny). The mutability of the different loci varied over a 9-fold range. When the different loci are ranked depending on their relative mutability (for spontaneous and induced mutations) it is found that in general, loci that mutate spontaneously relatively more frequently are also those at which more mutations have been recovered in the radiation experiments and likewise, those that are less mutable spontaneously are also those that mutate less after irradiation. Since the data are limited, it is concluded that the above finding is not inconsistent with the assumption of proportionality between spontaneous and induction rates of mutations. On the basis of the above results, a doubling dose of 100 R can be calculated for the X-ray induction of specific-locus mutations in Drosophila spermatozoa.
利用“Maxy”技术，在黑腹果蝇中研究了X射线对14个X染色体位点隐性可见特异性位点突变的诱导作用。对5日龄雄性果蝇进行3000伦琴的X射线照射，生殖细胞取样仅限于成熟精子。对在F1代中回收的推定突变雌性果蝇进行了雄性传递、等位性、育性和活力测试。在38898只雌性后代中回收的128个突变（115个完全突变和13个嵌合体，包括雄性存活和雄性致死的突变）被发现是可传递的。根据上述频率，平均突变率估计为7.8×10^(-8)/位点/伦琴；对于在雄性中存活且可育的突变，突变率为3.0×10^(-5)/位点/伦琴（38898只后代中有49个突变）。不同位点的突变频率范围很广：在raspberry和carnation位点未发现突变，而在其他位点，突变数从echinus位点的1个到garnet位点的31个不等；此外，雄性存活突变的比例也因位点而异。Schalet关于本研究中使用的14个位点中的13个位点自发突变的广泛数据，使得能够估计出自发突变率为6.1×10^(-6)/位点（490000只后代中共有39个突变）；对于在雄性中存活且可育的突变，突变率为3.0×10^(-6)/位点（490000只后代中有19个突变）。不同位点的突变性变化范围达9倍。当根据不同位点的相对突变性（自发突变和诱导突变）进行排序时，发现一般来说，自发突变相对更频繁的位点也是在辐射实验中回收突变较多的位点，同样，自发突变较少的位点也是照射后突变较少的位点。由于数据有限，得出的结论是，上述发现与自发突变率和诱导突变率之间成比例的假设并不矛盾。根据上述结果，可以计算出果蝇精子中X射线诱导特异性位点突变的加倍剂量为100伦琴。
