Naturwissenschaften 52(6): 142 (1965)
On the Radiomimetic Effect of Irradiated Desoxy-Ribonucleic Acid (DRAm) on Drosophila melanogaster
Institut fiir Allgemeine Biologie der Universität, Wien IX
Eingegangen am 3 Oktober 1964
During the last few decades, hundreds of chemicals have been tried for their mutagenic effect for Drosophila melanogaster. However, the chemicals that are mutagenically effective, are usually very toxic and lead to the death of the treated individuals. That DNA itself, in one form or another, could be mutagenic, has been known from "transformation" experiments1-5 for microorganisms and mammalian cells. The earliest experiments with Drosophila melanogaster were performed by GERSHENSON6a,b, who fed Drosophila flies on the culture medium to which calf-thymus DNA was added and claimed to have induced visible (viable) mutations in large numbers. There was no increase in the sex-linked-lethal rate. RAPOPORT7 and MULLER8a repeated Gershenson's experiments but could not reproduce the results.
SCHUSTER and SCHRAMM9 treated the RNA of the tobacco-mosaic-virus with nitrous acid and reported for the first time the mutagenic effect of the "in vitro" treated RNA. We thought it worth-while to investigate the mutagenic effect of the irradiated DNA (DNAm), particularly because DNA is abundant in nature and that the necessary changes could be produced by the natural ionizing radiations (Cosmic-radiation, natural and artificiaI radioactivity). To the knowledge of the present author, no investigations showing the mutagenic effect of irradiated DNA have ever been reported so far for Drosophila melanogaster or any other organisms.
For the purpose of the present investigations, the organism chosen was Drosophila melanogaster. Fish-sperm-DNA (in dry powder form) was irradiated with a dose of 100,000r at a rate of 625r/mt (180keV, 20m amps, 2mm A1 filter), added to the normal culture medium when warm and thoroughly mixed in. Adult Drosophila melanogaster flies of the Oregon-R strain (0 to 4 days old) were allowed to feed on this medium and lay eggs therein for 10 to 12 days and then discarded. The (males) emerging out of the larvae that had grown on this food were tested for the presence of the sex-linked-recessive-lethals (s.l.l.) by employing MULLER's C1B-technique and the autosomal recessive lethals (II-Chromosome) by employing stocks with dominant Lobe, Curly and Plum markers. In order to eliminate any possibility of the non-irradiated DNA being mutagenic or having any mutagenic contaminants, a parallel control experiment (for s.l.l.) was performed under exactly similar conditions, except for the difference that the added DNA was not irradiated.
Out of 635 DNAm-cultures, 36 were found to contain lethals, giving a s.1.1. rate of 5.7% as against 486 DNA-cultures where no lethals were detected at all. For the autosomal-recessive lethals out of 1436 DNAm-cultures 138 were found to contain lethals, giving autosomal-recessive-lethal-rate of 9.6%. In addition to this large increase in lethal rate, a number of visible mutations concerning the eye-colour, body-colour and body-size, abdominal malformation, wing-size and wing-form etc. were picked up. The number of malformed flies was particularly high though side effects of this nature were not rigorously recorded. The DNA-cultures, on the contrary, showed no such changes.
Taking the spontaneous mutation-rate to be 0.17%8b (just for the sake of comparison) the present experiment shows a 30-fold increase for the s.l.1, and a 60-fold for the autosomal lethals; this would correspond to a direct exposure of the sperm of about 2000 to 4000r of X-rays.
The present investigation definitely establishes the mutagenic effect of DNAm for Drosophila melanogaster. Further, DNAm is not toxic like most of the mutagenes and can arise in the body of the organism by the action of radiation on DNA of the body-cells (Internal-mutagene) and may be responsible for the somatic-mutations (cancers) on the hand and germinal-cell-mutations on the other (hereditary changes). It may arise outside and enter the body with food (External mutagene). In addition, DNAm might play an important role in the biological evolution. The possibility of injecting homologous or heterologous DNAm in animal experiments is an open field to be exploited. A detailed account of the present experiments will be published elsewhere.
The author wishes to thank Professors F. MAINX (Wien), H. J. MULLER (Indiana) and C. AUERBACH (Edinburgh) for valuable suggestions and constructive criticism. The DNA was supplied by Mayoly-Spindler laboratories, France, and the author acknowledges with thanks this generous help.
Nature 205, 312 - 313 (16
Induction of Sex-linked Recessive Lethals and Visible Mutations by feeding X-irradiated DNA to Drosophila melanogaster
Institut für Allgemeine Biologie, University of Vienna, Austria.
ATTEMPTS to induce genetic changes by chemical means go back to early days of modern genetical research. Even when Muller's1 discovery of the mutagenic effect of X-rays had opened up a new and exceedingly fruitful field of research, the search for chemical mutagens was not abandoned. In fact, during the last two or three decades, hundreds of chemicals have been tried for their mutagenic effect; however, most of these are highly toxic and are not found free in Nature. The search for a specific mutagen led Gershenson2,3 to try calf-thymus nucleic acid for its mutagenic effect. Gershenson reared flies upon food to which a large amount of (5 per cent) thymonucleic acid was added and found that a considerable number of the imagos, derived from the larvae that had had this food, showed various characteristic abnormalities. When these flies were bred, similar abnormalities were often found among their progeny. A large number of wing-mutations were claimed to have been induced by this treatment and this led him to claim that mutations had been produced en masse. Gershenson, employing ClB-technique, could not find any increase in the induction of sex-linked-lethals (s.l.l). Rapoport4 repeated Gershenson's experiments and he too could not observe any increase in s.l.l. rate. Muller5 tried both thymonucleic and yeast nucleic acids and did observe some phenotypic abnormalities but again no increase in s.l.l. To quote Muller: "It is hardly conceivable that a variety of types of visible mutations could be induced en masse by any agent without there being some appreciable effect on the lethal mutation frequency also". He was therefore of the opinion that there is no indication of either visible or lethal mutations induced by this treatment. On general considerations, one would not expect any harmful or mutagenic effect of the natural DNA, which forms an important part of the food consumed by every living organism. However, the possibility of such mutagenic effect of certain DNA's for certain organisms under given conditions could not be absolutely ruled out.