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Genetic X-radiation Damage to Drosophila Germ Cells under Different Conditions

Yonsei Medical Journal 1969년 10권 1호 p.25 ~ 36
 ( Yoon Jong-Sik ) - Yonsei University College of Medicine Department of Physiology

Abstract


Drosophila melanogaster (Oregon-R, Oak Ridge strain) males, 19 to 21 hours old, were-X-rayed with a total dose of 1000r. or 3000 r. given in two equal fractions of 500 r. or 1500 r. at a dose rate of 500 r. per minute, except for Experiment # 2 in which they were given a single dose of 1000 r. at 24±1℃ in several gas environments, with a time interval of 40 minutes between the two doses.
At each change of gas (es), the system was evacuated to remove all gases, then flushed with helium for 1 ;minute. Tests using CO were carried out in the dark .and the others in the light, both at l atmosphere of .the gas or gas mixture.
In order to study the genetic radiation damage and its modification by several gases the frequencies of dominant lethals and translocations induced in cells which were in different stages of spermatogenesis were scored using seven sequential 2-day matings -over a two-week test period.
Data are presented which indicate that :
1) The frequency of dominant lethals increased -from sperm to spermatids and meiotic cells, then decreased in spermatogonial cells which were the least susceptible to X-rays.
2) The cycle of damage for dominant lethals is similar to that for translocations, but does not coincide with it completely, and the peaks of damage for both are located in the early postmeiotic stages, and the cycle of frequencies of translocations coincides with that of percentages of sterility of F₁. The coincidence of frequencies between translocations and the sterility demonstrates that the mechanisms of damage for both are related, at least in part.
3) The NO effect on sperm and late spermatids is more drastic than the oxygen effect, but a major fraction of the effect is to cause the death of the sperm.
4) The carbon monoxide (CO) during radiation increase genetic damage above the other gases tested, and it is possible to conclude that the duration(s) of 4 minutes of gases in post-treatments is too short to modify the damage.
5) There are few (or no) translocations recovered from premeiotic cells.
6) The Y-chromosome was involved in 10.8 % of total breaks, or about 1 /4 as frequently as the two autosomes tested, and chromosomes 2 and 3 equally participated in an interchange.

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