Sex-linked Recessive Lethals Research Articles

RBE values of 15-MeV neutrons for recessive lethals and translocations in mature spermatozoa and late spermatids of drosophila

Frequencies of sex-linked recessive lethals (in the X C2 chromosome) and of translocations between the second and third chromosomes in Drosophila melanogaster were determined after irradiation of mature spermatozoa and late spermatids with 15-MeV neutrons and 250-kV X-irradiation. The doses employed ranged from 1200–4000 rad. The results show that, at all dose levels, neutrons are more effective than X-rays in producing genetic damage in late spermatids than in mature spermatozoa. The effect is more pronounced for translocations than for recessive lethals; at translocation frequencies of 2–4%, neutrons are about twice as effective in spermatids as in sperm. These observations are consistent with the finding that the lower sensitivity of late spermatids to X-irradiation originates from their lower degree of oxygenation than sperm. The greater effectiveness of neutrons in producing chromosomal damage in these relatively anoxic cells, is therefore another indication of the potential advantage of neutrons over X-rays in the treatment of tumours. The relatively low RBE values obtained for 15-MeV neutron irradiation in this study are discussed in the context of what has been recorded in the literature. The apparent discrepancies between the present and the earlier results seem to arise both from a possible mixing of stages with different X-ray sensitivity and from using neutrons of different LET spectra in the earlier work.

Triclosan as a Genotoxic Compound for <i>Drosophila melanogaster</i>

Triclosan [5, chloro-2-(2, 4-dichlorophenoxy) phenol] (CAS No. 3380-34-5) is extensively used as an antimicrobial agent in many pharmaceutical formulations. Understanding its genotoxic potential is the aim of this experimental study. Drosophila fulfils dual function in the field of genetic toxicology - firstly as an experimental organism for short term tests to identify carcinogens and secondly as a model for learning mechanistic pathways of mutagenesis induced by environmental toxicants. The mutagenesis in Drosophila melanogaster contributed by triclosan is the theme of this study. The Sex-linked recessive lethal (SLRL) test was conducted on stock of Drosophila melanogaster. Males of well-defined stock and appropriately marked balancer females of FM 7 stock with multiple inverted X-chromosomes were used for the experiment. The triclosan concentration was administered with exposure concentration ranging from 0.5 to 2 mg for adults. The results indicated significant reduction in the number of males in the F2 generation. The mortality of larval population was 100% suggesting the test required lowering of concentrations of triclosan that was administered particularly with respect to larvae. DOI: 10.3126/kuset.v4i1.2879 Kathmandu University Journal of Science, Engineering and Technology Vol.4, No.1, September 2008, pp 12-16

Genetic effects of tritiated thymidine and evidence for its incorporation into a cytoplasmic component of the adult testis of Drosophila Melanogaster

Sex-linked recessive lethals were induced by the injection of [ 3H]thymidine into male imagos of Drosophila melanogaster. Elevated mutation rates were observed earlier than the tenth day post-injection when the first labeled sperm cells are expected to be available for fertilizations. Radioautographs prepared from testes of males taken from successive broods disclosed a cytoplasmic label which was removable by DNAase. It is suggested that radiations from the labeled cytoplasmic DNA were responsible for the mutations produced in the early broods. The nature of the cytoplasmic body which had incorporated the [ 3H]thymidine is not known.

Spontaneous sex-linked recessive lethal frequencies from aged and non-aged spermatozoa of Drosophila melanogaster

A standardized sample of spermatozoa from Drosophila melanogaster males was tested for spontaneously occurring F 2 and F 3 sex-linked recessive lethality before and after 3 weeks aging. F 2 increased in sperm stored in females at 26° at the rate of 0.047% of lethals per week, however, F 3 lethal frequencies were approximately the same in the aged or non-aged experiments. The frequency of spontaneously occurring mosaic lethality was small when small compared to the total F 3 mutations measured and it seems unlikely that any slight effect of aging could have been measured. Approx. 41% gonadal tissue was producing lethal gametes when all mosaic lethals were considered, however, in a single case the percent lethal tissue could be either much greater or much less than this value.

The lowering effect of dose-fractionation on recessive lethal frequencies in Drosophila spermatocytes

The effect of dose-fractionation on the induction of sex-linked recessive lethals in a ring-X chromosome was studied in he different stages of spermatogenesis of Drosophila melanogaster. The fractionated dose was given in five fractions at 2-h intervals. In some experiments the fractionation was combined with pre- or post-treatments with nitrogen or oxygen. In cells presumably corresponding to spermatocytes dose-fractionation resulted in a significant decrease of the mutation frequency. The fractionation effect in spermatocytes was also significant when dose-fractionation was combined with pre- or post-treatments with nitrogen. As the most likely interpretation for the fractionation effect, I presume that the acute and fractionated radiation differentially affect a process of cell selection.

Temperature-sensitive mutations in Drosophila melanogaster,I. Relative frequencies among gamma-ray and chemically induced sex-linked recessive lethals and semilethals.

Temperature-sensitive mutations in Drosophila melanogaster,I. Relative frequencies among gamma-ray and chemically induced sex-linked recessive lethals and semilethals.

Differential mutagenicity of the amine and amide derivatives of nitroso compounds in Drosophila melanogaster

The mutagenicity of N-diethyl- N-nitrosamine (DEN) was compared with that of N-ethyl- N-nitrosourethane (ENU) as regards: non-disjunction, XO males, translocations, induced crossing-over in the male, sex-linked recessive lethals and the elimination of y + and B from a marked Y-chromosome. All phenomena were followed in daily sperm samples from injected males (30 ± 5 h old) bred at unity mating pressure (equal male to female ratio). The various genetic effects were simultaneously determined on the same sample of treated cells or testes, so as to enable the assessment of the relative yield of different mutations. Activity as regards non-disjunction was low with both compounds, but there were occasional indications of some rise in its frequency within the 11th–14th days, thus marking the period of utilization of the meiotic spermatocytes. Induced crossing-over was first sampled on the 10th or 11th day; small clusters of identical or complementary recombinants occurred on the 12th–14th days and the larger ones from the 15th day. Accordingly, the post-meiotic sector of the germ line (sperm and spermatids) was sampled during the first 9 days and the pre-meiotic (spermatocytes and spermatogonia) from the 10th day onwards, with the gonia mainly starting on the 15th day. The yield of the sex-linked recessive lethals was roughly the same for the pre- a and post-meiotic stages with DEN, but was considerably higher for the more mature stages with ENU. There was virtually no activity with either compound as regards the induction of chromosome breaks: both did not induce XO males, and were inactive for translocations. Deletion of the Y-markers occurred with both compounds, but was almost restricted to the pre-meiotic stages with DEN, while extending to the post-meiotic sector with ENU. The induction of deletions relative to lethals with both compounds was higher for the pre- than for the post-meiotic sector, but the degree of this differential response was more marked with DEN. The differences in the mutagenicity of the tested compounds were discussed in relation to their biochemical properties and carcinogenic effects.

RBE schneller neutronen bei der Auslösung von Mutationen bei Drosophila melanogaster

The RBE of fast neutrons (as compared with X-rays) was determined in Drosophila melanogaster for various “broods” (stages of germ cells) and for sex-linked recessive lethals as well as for translocations between 2nd and 3rd chromosome. A pronounced dependence of RBE on the stage of the germ cells was shown to occur and to account for most of the discrepancies reported in earlier work. Moreover, the RBE was demonstrated to be lower for recessive lethals than for translocations at all stages of spermatogenesis tested. These findings are discussed briefly as to their implications for problems of protection from radiation damage. A more fundamental discussion is, however, not entered into since it could only lead to speculation.

Mutagenic activity in Drosophila of two pyrrolizidine alkaloids

The data on mutagenicity are shown in Table 1. Both fulvine and retrorsine show moderate activity, falling into Clark’s (1960) second category. Isatidine, the N-oxide of retrorsine is much less active than the base itself, a result which is consistent with those of Clark. Monocrotaline and fulvine induce translocations, but at a rate which is very low compared with the incidence of sex-linked recessive lethals (cf. Avanzi, 1961; Clark, 1963).

The mutagenic properties of the nucleosides of pyrimidine analogues in Drosophila melanogaster

The mutagenic activity of the 5-halogen derivatives of deoxyuridine (FUdR, BUdR and IUdR), cytosine arabinoside (CA), 6-azauridine (AzUR) and 6-azacytidine (AzCR) were tested on the male germ line of Drosophila. All compounds were inactive as regards the induction of point mutations (sex-linked recessive lethals and visibles). They were also virtually ineffective in the induction of viable chromosome rearrangements; the highest yield of X-chromosome fragments occurred with IUdR, but only reached a rate of 1 per 10 4 treated gametes. The only mutations induced at an appreciable rate by the tested nucleosides were the small chromosome deletions resulting in the Minute phenotype. Maximal activity in this respect was of the order of 5 mutations per 10 3 treated sperm and was obtained at an injected concentration of 2·0 × 10 −2 M; further increase in dose did not raise the mutation rate. Mutagenic activity was roughly the same for compounds that could enter DNA (BUdR, IUdR and CA) as with those which were not expected to do so (FUdR, AzUR and AzCR). Activity was higher on cells that could undergo nucleoprotein synthesis and chromosome replication (spermatocytes and spermatogonia) than on stages that were inert in this respect (spermatids and sperm). The damage induced consisted of chromosome deletions involving more than one band of the salivary gland chromosome, suggesting the elimination of several DNA molecules. The chromosome breaks leading to the deletions extended across both chromatids, since the resulting Minutes were almost exclusively complete (non-mosaic). The distribution of the Minutes among the chromosomes was somewhat more preferential for the IVth chromosome with the tested compounds, except CA. Consideration was given to the possible genetic hazards to man involved in the chemotherapeutic use of IUdR, AzUR and AzCR. Attention was drawn to the fact that long term genetic hazards were mainly caused by the rise in point-mutations, which persisted for many generations in the human gene pool. Such hazards would not occur with the nucleosides since they were virtually inactive as regards the induction of intragenic changes. Nevertheless, the small chromosome deletions which these agents produced, were expected to result in short term genetic damage in the treated patients and their offspring.

The mutagenicity inDrosophila melanogaster of caffeine and of other compounds which produce chromosome breakage in human cells in culture

1. Actinomycin D failed to raise the mutation rate and did not cause chromosome loss although it induces chromatid breakage and translocations in human cells in culture. 2. Mitomycin C, an alkylating agent, caused preferential killing of the treated male larvae (somatic damage), chromosome loss, and sex-linked recessive lethals. 3. Proflavin was not mutagenic or only slightly so and did not kill treated ♂ ♂ larvae preferentially. The non-disjunction rate was slightly increased. 4. Simultaneous exposure of the larvae to proflavin and caffeine eliminated the proflavin-induced increase in non-disjunction. 5. Caffeine treatment ofDrosophila larvae caused differential mortality of the treated larvae (preferential killing of maleDrosophila). It induced X-chromosome loss and sexlinked recessive lethals after treatment of female larvae. The effect on males was not tested. The non-disjunction rate following caffeine treatment was somewhat reduced. 6. The differential mortality ofDrosophila larvae after exposure to mutagenic agents can be used for the preliminary screening of agents which might be mutagenic and are used by man, as was already proposed byOster. 7. These results are discussed in relation to parallel studies on chromosome breakage by the same substances in human cells in culture.

Lack of Mutagenic Effect of Irradiated Drosophila Medium

THE possibility that irradiated food may be mutagenic gains great importance from the widespread use of radiation for the preservation of food. Stone et al.1 have found increased mutation frequencies in Staphylococcus aureus which had been cultured in ultra-violet-treated medium. More recently, there have been reports2–5 on cytological abnormalities in plant roots that had been kept in X-rayed culture fluid. Recent experiments on Drosophila6 have indicated that the incidence of sex-linked recessive lethals and visible mutations may be enhanced by feeding the larvae on irradiated medium. In view of the practical importance of this possibility, a large-scale experiment was carried out to test the genetic effects of irradiated food on Drosophila melanogaster.

INDUCTION OF SEX-LINKED RECESSIVE LETHALS AND VISIBLE MUTATIONS BY FEEDING X-IRRADIATED DNA TO DROSOPHILA MELANOGASTER.

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.

Radiosensitivity of the stages of spermatogenesis to different mutations in Drosophila melanogaster

The induction of sex-linked recessive lethals, XO males and chromosome deletions were followed relative to non-disjunction (XXY females) and induced crossing-over in daily sperm samples from irradiated males. Non-disjunction marked the sampling of meiotic spermatocytes (prior to and during anaphase I) and its yield was highest on the 10th–12th days, although a low rate occasionally occurred as early as the 8th (once in 12 experiments) or as late as the 13th day. Accordingly, post-meiotic stages (sperm and spermatids) were mainly used during the first 9 days, and meiotic and pre-meiotic stages (spermatocytes and spermatogonia) were sampled starting from the 10th day. Induced crossing-over marked the utilization of diploid germ cells (spermatocytes and spermatogonia) and was substantially sampled on the 10th and later days. Small “clusters” of recombinants involving the same chromosome site occurred 12–13 days after treatment, possibly indicating the sampling of spermatogonia late in the mitotic cycle. The induction of sex-linked recessive lethals and XO males was high in the spermatid stages (6–9 days) and decreased sharply in frequency with the increase in the rate of non-disjunction. The response for these mutations, therefore, was considerably lower in meiotic spermatocytes than in early spermatids. The mutation rate for the deletions ( γ + and B from the Y-chromosome) reached its peak before that of non-disjunction but remained high during the sampling of the latter aberrations. Radiosensitivity to the induction of deletions, therefore, although highest in the early spermatids, did extend to the late meiotic spermatocytes.

The relationship between radiation dose and mutation frequency in spermatogonia of Drosophila melanogaster

Data are presented on the rate of induction of IInd chromosome recessive lethal mutations in Drosophila melanogaster following irradiation of spermatogonia with 60Co γ-rays over a dose range 200–800 rad. The dose-response was linear, the line of best fit being γ = 0.455 + 1.33 × 10 −3 x. The data are discussed in relation to recent work on sex-linked recessive lethals reported by Oftedal 4 and by Abrahamson and Friedman 1. It was concluded that the linear dose-response reported in this paper resembled that observed by Abrahamson and Friedman at high radiation doses. Furthermore, these data were not incompatible with the non-linear response reported by Oftedal at low radiation doses.

Genetic effects of spermatogonial X-irradiation on productivity of F 1 female mice

1. (1) Hybrid male mice were given two doses of 600 R high intensity X-rays eight weeks apart and outcrossed 12 weeks after the second dose. Daughters were also outcrossed and effects on their productivity studied by obtaining data from their first 4 litters at birth and from their fifth at about the 14-day foetal stage. Controls had exactly the same treatment apart from the irradiation. 2. (2) The average number of liveborn per tested female fell by 4.8% from 26.0 in the controls to 24.7 in the irradiated series. The mean litter-size fell significantly by 5.5%. 3. (3) The main factor reducing productivity was inherited semi-sterility in 6.7% of daughters of irradiated males, with none in controls. When combined with data on sons of the same irradiated males this gives an estimated rate of induction of translocations in spermatogonia of 6.4.10 −5/genome/R after two doses of 600 R. This is about one-sixth that reported for spermatozoal irradiation at similar single doses. It is suggested that this differences is mainly due to differential radio-sensitivity of spermatogonial mitotic stages, with only the most condensed stages having a similar sensitivity to that of spermatozoa. 4. (4) The sex-ratio at birth fell significantly from 52.0% in progeny of control daughters to 49.4% in the irradiated series. Other data, however, gave little evidence for the action of recessive sex-linked lethals, or teh presence of XO mice. It was concluded that the sex-ratio decrease was probably due mainly to other unknown causes and that a large-scale experiment with sex-linked markers is necessary if the rate of induction of sex-linked lethals is to be accurately determined. 5. (5) Dominant sub-lethality, sterlity or reduced fertility other than semi-sterility did not seem to play part in the reduction of productivity in daughters of irradiated males.

NONRANDOM DISTRIBUTION OF LETHALS INDUCED BY TRITIATED THYMIDINE IN DROSOPHILA MELANOGASTER.

Mutations were induced in Drosophila males by tritiated thymidine fed to larvae or injected into adults. Radioautographs of testes of treated males demonstrated a correlation between the occurrence of mutations and the presence of labeled sperna bundles. In addition to the presence of sex-linked recessive lethals, dominant lethals were also measureable. Mapping of the induced sex- linked recessive lethals disclosed a nonrandom distribution which differed from reported distributions of mutations induced by x rays and gamma rays. Distribution of mutations induced by H/sup 3/T appears to reflect the varying frequency with which thymine bases occur along the lengih of the Drosophila X chromosome. (auth)

DOSE RATE EFFECTS IN THE DEVELOPING GERM CELLS OF MALE DROSOPHILA.

The developing germ cells of Drosophila melanogaster were treated with fast and fractionated doses of x radiation in 4 atmospheres of argon or in 3 atmospheres of argon + 2 atmosphere of oxygen. An enhancement in biological damage was observed in all postmeiotic sperm and spermatid cells in tests when oxygen was present in combination with argon. There were no effects due to the rate at which the radiation was administered with mature sperm cells. Enhancements in translocations and sex-linked recessive lethals were obtained for spermatids in argon by giving the total radiation dose in two fractions 40 minutes apart. When oxygen was present with the argon, similar values were obtained with a fast, continuous dose and with fractionated doses. Another type of dose rate effect was observed when spermatogonia were treated. The dominant lethal percentages were higher when doses were fractionated in both the argon and in the argon + oxygen tests. (auth)

THE FAILURE OF SULPHHYDRYL COMPOUNDS, AET, MEA, AND GLUTATHIONE TO PROTECT AGAINST X-RAY INDUCED CHROMOSOME ABERRATIONS IN MALE DROSOPHILA.

SummaryPre-treatment with the mammalian radioprotective sulphhydryl compounds AET, MEA, and glutathione did not protect the Drosophila testis from radiation-induced genetic damage. Protection was not given to spermatozoa, spermatids, spermatocytes and spermatogonia. The responses measured were production of recessive sex-linked lethals, translocations, deletions, loss of X and Y chromosomes and ‘dominant lethals’. MEA increased the recessive lethals in the 3–6 day brood. Pre-treatment with glutathione increased the incidence of XO males in the 6–9 day brood and post-treatment in 0–3 day brood. MEA and glutathione increased the percentage of eggs that failed to develop in ‘dominant lethal’ tests.

INDUCTION OF MUTATIONS AND KILLING OF CELLS IN IRRADIATED SPERMATOGONIA OF DROSOPHILA.

IN experiments where Drosophila melanogaster spermatogonia were irradiated in the 20-h old embryo with doses of 0 r., 55 r., 110 r., 160 r. and 310 r. given at 25 r./min, and the induction of sex-linked recessive lethals observed, a non-linear dose effect curve was found1. This curve had a rather flat maximum for doses of 110 r. and 160 r. (about 0.15 per cent lethals above controls), whereas 310 r. gave no increase in lethal frequency above the control value. These results were based on slightly more than 100,000 X-chromosomes tested (Fig. 1).