November 1957 NOTES Mfl) NEWS 107 RESEARCH NOTES Athan
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November 1957 NOTES Mfl) NEWS 107 RESEARCH NOTES Athan MurvelE, Effects of Virgin D. melanogaster (Oregon-R) derdation on X_ra.r_induced females, 24 to 43 hours old, were damage to Drosophila females, placed either in a desiccating chamber or in a moist chamber. After 8 hours of this treatment, they were exposed to 5000, 2500, or 0 roentens of X-rays. Immediately after exposure, each female was placed in an individual container with two males. Every day following treatment (for 10 days), two individual females from each of the six treatment groups (2 degrees of dehydration and 3 decrees of irradiation) were selected randomly to be sacrificed for ovarian examinations. The ovaries were examined for cuantitative enumera- tions of stages 5 and 10 of ogenesis (after King, et al., GR0H, 1956) for 10 days following treatment. The data are too few to permit drawing general conclusions on the effects of X-rays on frequencies of stages of ogenesis. In none of the data were there any significant deviations due to the dehydration treatment. Herskowitz (L)IS, 1956) found that dehydration increased X-ray-induced egg mortality. Although the deviations due to dehydration in our results were not statistically significant, the mean values were in the opposite direction; that is, dehydration tended to decrease egg mortality. This failure to duplicate Herskowitz's results may have been due to our use of a different degree of dehydration or different-aged females. Further work is under way to find possible effects of degree of dehydration on X-ray-, induced damage to D. melanogaster females, (This research was supported by U.S.?.H.S. grant RG-4626,) Aslaksen,Erik, Pleiotropic The mutant red used in this experiment pattern of the mutant red was received from I. Oster, and the (red Malpighian tubules) in investigations were carried out D. melanogas -ber, together with E. Haclorn in Zurich. We found that the red eye pigment and the content of isoxanthopterine are decreased in this mutant compared to what is found in the wild type. This is compensated for by an increase of other pterines. The red pigment in the Malpighian tubules is found to he an ommochrome, but is not the same as that found in the eyes. In experiments on transplantation of eye discs, the mutant red exhibits autonomous development with respect to the amount of red pigment. Auerbach, C. The production . In view of the personal factor involved of visible muta:bions by in the scoring of visible mutations, ci1oroethyl methane suiphonate it seems important to obtain independent (CB 1506). information of the claim that some alkylating agents produce very high frequencies of visible mutations, many of which have not occured previously. In Muller-5 experiments by the Fahmys, CB 1506 produced an over-all ratio of 4 visible to 10 lethal recessives, and in later broods from sensitive spermatogonia this ratio increased to near unity. In the experiments to be presented here, 1- to 3-day-old OrK males were injected with a 10 2 M solution of CB 1506, They were then mated to a succession of virgin females at intervals of 3-4 days. In broods d (days 11-14) and e (15-18), half the 108 Notes andNews - Research DIS31. males were mated to 3 M-5 females each and half to 3 X)C= females each; males which had been given one type of female in d were given the other type in e The sons by Th= females were carefully examined by myself at lOx magi.ifica- tion, and all deviants were progeny tested. The F2 vials of the. Muller5 tests were examined without etherization through a binocular. This was done by a laboratory assistant, who was told to look carefully for visibles, She was. chosen for the job because she has had over 10 years' experience with flies, uses a higher magnification for scoring lethals than is customary in our laboratory, is unusually observant and as a rule detects more visibles in M-5 tests than I do, A summary of the results is tabulated. The figures in brackets refer to males which for some reason or other could not be progeny tested. The column "Exp. 1" states the number of lethals which, on the basis of the parallel M-5 test, would be expected in a progeny of the size sampled, c? M-5 'c xx= Brood niVis. Vis. ii Exp. 1 Vis, %.Vis. d 386 21 2 0.5 864 47 6 (8) 7 (i,$) e 379502 0.5 -- 87811527 (3) 32 (34) In the Muller-5 tests the ratio of visibles to lethals was about 1 : 17, that is, within the range found in X-ray experiments ir which similar scoring methods were used, including experiments carried out by us. It is very much below the 4 10 ratio found by the Fahmys. In the XX= tests the percentage of visibles was higher, presumably for two reasons. (i) Even very slight abnormalities could be detected. (2) Many of the detected mutants had poor or very poor penetrance in progeny tests, and these would have excaped notice in M-5 tests. In brood e, only 10 of the tested mutants were fully penetrant, and if those alone are used the percentage of visibles drops to 1.1. My results, therefore, do not confirm the finding by Falzny and Fabmy. This does not, of course, invalidate their observations; but itshow's that definition of what constitutes a visible mutation, methods of scoring, and powers. of observation differ considerably between laboratories and workers. Judged by my results in X-ray tests, my standards are roughly similar to those used by the earlier X-ray workers. That the Fahmys used higher ,.standards is shown by the fact that In X-ray experiments by the Muller-S method, in hich the F2 cultures were "scored under a low-power binocular without etherization rather early after emergence," they found the same ratio of 2 visibles to 10 lethals which Spencer and Stern obtained in experiments in which every culture was etherized and examined under the binocular.. Incidentally, it will be of interest to see the detailed data on which the Fahniys base their conclusion that the ratio of 2 visibles i 10 letha]-s in their X-ray experiments, differs significantly from the over-all ratio of 3 visibles : 10 lethals in exDeriments with phenyl alanine niutard. According to the table published in pIS.-28, this latter ratio fluctuates between 1.8 : 10 and 38 : 10. when series containing less than 400 tested chromosomes are excluded. An additional source of discrepancy between the findings of the Fahmys and myself may be that I counted visibles which occurred in clusters as so many single mutations,. because obiously in these broods the noriniutated germ cells may also have occurred in clusters. The Fahniys, on the other hand, counted each cluster as a single mutation, and corrected the frequency of lethals "on the basis of the frequenoie. of November 1957 Notes and News - Research 109 identical visibles in each brood." If this correction was done on the basis of the largest observed cluster it must have resulted in an underestimate of the lethal frequency. Moreover, lethals, many of which are subject to germinal selection, might be expected to form smaller clusters than visible viable mutations. The nature of the visible mutations which occurred in the experiment with GB 1506 was not striking. There were alleles of Cu, £ and w, and in addition a number of unidentified mutations to rough eyes, smaller body size s and spread or drooping or incised wings. The one striking fact was that two mutations occurred repeatedly in the progeny of different males. One was a satsuma-like allele of w, which occurred twice. According to an analysis, kindly carried out by Dr. M. M. Green, the two mutants are indistinuishaL1e phenotypically and in their interactions with "zeste" and with the enhancer of w 0 ; they are thus probably identical. The other case was that of a mutation to rotated abdomen (not yet located accurately), which occurred twice independently in the experiment described above, a third time in another experiment with GB 1506, carried out on a different strain of males, and a fourth time in a recent experiment with mustard gas. These recurrences point to the possibility that some mutational steps occur more readily then others under the influence of GB 1506 and possibly, of other niutagens with chloroethyl groups. Auerbach, C., and Fabniy and Fahmy found that injection Sonbati,E.M. The of GB 1506 into adult males produces brood pattern of very low mutation frequencies in mutations after early broods and very high ones in late treatment with broods. Possible causes of this chloroethyl methane unusual brood pattern are slow action suiphonate (GB 1506). of the chemical, long mutational delay, dependence of the mutagenic action on cell' division or on rate or type of metabolism. These possibilities have been explored in a number of preliminary experiments. (1) Treated spermatozoa were stored in males or inseminated females, and mutation rates were scored (a) in progeny obtained during the first days after treatment, (b) in progeny from stored spermatozoa, (c) in progeny from males which had been kept with females for the periods of storing used in group (b). Mutation rates in (b) were intermediate between those in (a) and (o). Slow mutagenic action and/or mutational delay are thus only contributory causes of the brood pattern. With periods of storing exceeding 12 days, mutation frequencies dropped again, presumably because of selection against males or spermatozoa which had absorbed more than the average amount of niutagen.