Sankaranarayanan K
Mutat Res. 1982 Feb 22;92(1-2):139-49. doi: 10.1016/0027-5107(82)90218-4.
A series of X-irradiation experiments was carried out using Drosophila melanogaster females homozygous for a third chromosome mutator gene and females which had a similar genetic background except that the mutator-bearing third chromosomes were substituted by normal wild-type chromosomes. The mutator females had been previously shown by Gold and Green to manifest a higher level of radiation-induced mutability (as measured by the X-ray-induction of sex-linked recessive lethals) in their pre-meiotic germ cells compared to normal females at an exposure of 100 R. In the presence work, the sensitivity of the pre-meiotic germ cells of mutator and normal females to the X-ray induction (2000 R) of sex-linked recessive lethals was studied. In addition, experiments were conducted to examine the sensitivity of the immature (stage 7; prophase I of meiosis) oocytes of both kinds of females to the induction of dominant lethals, X-linked recessive lethals and X-chromosome losses. The result show that in pre-meiotic germ cells, the frequencies of radiation-induced recessive lethals are similar in both kinds of females. However, the proportion of these mutations that occur in clusters of size 3 and higher, is higher in mutator than in normal females. In stage-7 oocytes, the frequencies of radiation-induced dominant lethals and sex-linked recessive lethals were similar in both kinds of females. The X-loss frequencies however, were consistently higher in mutator females although statistical significance was obtained only at higher exposures (3000 and 3750 R) and not at lower ones (750-2250 R). Possible reasons for the discrepancy between the present results and those of Gold and Green with respect to pre-meiotic germ cells are discussed.
利用黑腹果蝇进行了一系列X射线照射实验。实验对象为纯合有第三条染色体突变基因的雌性果蝇，以及除携带突变基因的第三条染色体被正常野生型染色体替代外，具有相似遗传背景的雌性果蝇。此前，戈尔德和格林已证明，在100伦琴的照射剂量下，与正常雌性果蝇相比，携带突变基因的雌性果蝇在减数分裂前的生殖细胞中表现出更高水平的辐射诱导突变率（通过X射线诱导性连锁隐性致死突变来衡量）。在本研究中，研究了携带突变基因和正常雌性果蝇减数分裂前生殖细胞对X射线诱导（2000伦琴）性连锁隐性致死突变的敏感性。此外，还进行了实验，以检验这两种雌性果蝇未成熟（第7阶段；减数分裂前期I）卵母细胞对显性致死突变、X连锁隐性致死突变和X染色体丢失诱导的敏感性。结果表明，在减数分裂前的生殖细胞中，两种雌性果蝇辐射诱导的隐性致死突变频率相似。然而，突变体中发生在大小为3及以上簇中的这些突变比例高于正常雌性果蝇。在第7阶段卵母细胞中，两种雌性果蝇辐射诱导的显性致死突变和性连锁隐性致死突变频率相似。然而，突变体雌性果蝇的X染色体丢失频率始终较高，尽管仅在较高照射剂量（3000和3750伦琴）下获得了统计学显著性，而在较低照射剂量（750 - 2250伦琴）下未获得。讨论了本研究结果与戈尔德和格林关于减数分裂前生殖细胞的研究结果之间存在差异的可能原因。
