120.キイロショウジョウバエ卵母細胞のマイクロ波被曝によるX-染色体の不分離の誘発
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Tis study was conducted using Drosophila melanogaster oocytes as one of a series of experiments to ascertain the effects of microwaves on living bodies. Fujikawa et al. reported in 1994 that treating Drosophila melanogaster oocytes with carbon dioxide induced sex chromosome non-disjunction. The effects of microwaves on living bodies may be confirmed if exposing oocytes to microwaves generates more heteroploidies of sex chromosomes than those generated in the control group. Materials and Method Used: The present author obtained yw^iec/B^sYsc^8 y stocks (female adults used for microwave-exposure test) and mwhjv; spa^<pol>+stocks (male adults). Oocytes of P (y stocks, female parent) were exposed to microwave (using a home-use microwave oven, with a frequency range of 2.45GHz) for 5 seconds and for 10 seconds with an output of 500W and for 60 seconds with 200W. The non-disjunction of X chromosomes was detected in F_1 using the following steps. Results and Discussion: The phenotype of y-stock females had yellow bodies and ivory-colored eyes, while the+stock males had wild-type-color bodies and red eyes. Next-generation female flies from the mating those with red eyes had wild-type-color bodies and red eyes while males had yellow bodies and ivory-colored eyes. However, if sex chromosomes non-disjunction is induced, females will have XXY sex chromosomes; that is, flies with phenotypes will have yellow bodies and ivory-colored eyes. Male flies will have XO sex chromosomes, wild-type bodies, and red eyes. The results of the experiment are shown in Table 1. Out of 5511 flies of the control group, F_1, there were two females and three males due to the induction of sex chromosome non-disjunction. Out of the 3768 F_1 flies exposed to microwaves for five seconds with an output of 500W, these emerged four females and one male, while out of the 3148 flies exposed to 500W for 10 seconds, one female and two males emerged; out of 935 exposed to 200W for 60 seconds, only one male with non-disjunction was induced. No difference was found in the number of heteroploidies between the control group and the experimental group. The results suggest that there were no effects of microwave exposure on sex chromosome non-disjunction. It is clear from the above experiment that there were no effects of microwave exposure on oocytes, although a slight difference was noted in the number of F_1 flies due to trauma caused by the difference in output of the microwave oven or the duration of exposure (Table 1). The present author thinks that an additional experiment is required one in which oocytes exposed to X-rays are used as a control group, in order to verify the results of this experiment. Fujikawa et al. reported in 1994 that the frequency of F_1 heteroploidies increased in the experimental group when oocytes were treated with carbon dioxide for 45 minutes or longer during the metaphas of the first meiotic division. They pointed to the non-disjunction induction mechanism caused by carbon dioxide as the reason for this phenomenon. They also suggested that extracellular CO_2 plus oxygen deficit evoke cellular conditions that damage the spindle body and thereby affect the normal segregation of homologous chromosomes later. They also reported that they had a negative result from a similar experiment using oocytes exposed to X-rays.
- 1996-03-15
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