Walking ability of Drosophila melanogaster was measured by Benzer's countercurrent apparatus. Second chromosomes isolated from a natural population carried much variation in walking abilities when examined in the dark, in the light and toward the light source conditions. Walking abilities in the three conditions were positively correlated both in the homozygotes and heterozygotes, and were mainly controlled by additive polygenes.
A gene, Lethal hybrid rescue (Lhr 2-95), which rescues the lethal hybrids between Drosophila melanogaster and D. simulans was found on a second chromosome of D. simulans from a natural population. The cross, melanogaster _??_×simulans _??_, which normally produces only female progeny, resulted in the production of both female and males at an equal frequency when the simulans males carried Lhr. The reciprocal cross, simulans _??_×melanogaster _??_, which ordinarily produces only males, gave rise to about 14% females and 86% males. The cross, XX/Y melanogaster _??_×simulans _??_ carrying Lhr, produced a few percent females, although normal simulans produced only hybrid males. The sex ratio (SR) factor and daughterless (da) gene killed either hybrid males or hybrid females according to their usual actions, showing no specific interactions with the Lhr gene. All hybrids, those rescued by Lhr as well as those produced normally, were completely sterile. Evolutionally implications of Lhr are briefly discussed.
Effect of caffeine on the frequency of 8-azaguanine (8AG) resistant mutation in Chinese hamster cells (V79 cells) treated with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), was investigated. The results showed that the effects of caffeine appeared to be different in manner depending on the time and duration of caffeine exposure after MNNG treatment. (1) When the cells were exposed to caffeine during the first half of mutation expression time (0-24h after MNNG treatment), the mutation frequency was slightly enhanced compared with MNNG treatment alone. (2) On the contrary, mutation frequency was reduced if caffeine was present during the latter half of expression time (24-48h after MNNG treatment). (3) Caffeine drastically reduced the frequency of mutation if the cells were exposed to caffeine for the whole mutation selection period from 48 to 240h after MNNG treatment.
Adult flies of a bw; st ss strain exhibited an anomalous response (jumping behaviour) to light at the moment the light was intercepted by a hand or the light being turned off. We named the response pyokori (a Japanese word for a jumping in surprise). On the other hand, a Hikone-H wild strain did not show such a response. The pyokori behaviour is determined by a recessive gene(s) located on the second and the third chromosomes. It is necessary that, in order to show the pyokori response, flies must be homozygous for a gene(s) located on the second chromosome and minor gene(s) on the third. The degree of pyokori response was markedly influenced by the intensity of illumination, the wavelength of light, and the age of flies used. After emergence, the flies kept in dark (0 lux) or under high intensity illumination (3000 lux) showed almost no pyokori response. On the other hand, newly emerged flies kept under a low light (50 lux or 100 lux) increased the pyokori response to an upper limit of 3 days. Under 200 lux, 1000 lux, 1500 lux of illumination, the pyokori response increased gradually for the first 16, 10, or 6 hours after emergence, respectively, then it decreased rapidly until the response disappeared almost completely by 24, 16, or 12 hours after emergence, respectively. When the flies were kept under an intensive light for a few days, not only the pyokori response but phototaxis disappeared nearly completely in the bw; st ss strain. In such flies, almost no ERG was observed. Normal ERG pattern was observed in the flies kept under the red light or in the dark and 50 lux or 100 lux white light condition for a long time. The Hikone-H wild flies showed normal ERG in any light condition. From these results it may be supposed that the pyokori behaviour in bw; st ss strain has an important relationship with the existence of photoreceptor or photopigment in ommatidia of compound eye.
Wild and cultured populations of the Pacific oyster, Crassostreagigas, were analysed by starch gel electrophoresis for catalase (CAT). The comparison of genotypic frequencies at the Cat locus revealed an apparent advantage of heterozygotes in the wild and cultured populations. The observed frequency of heterozygotes in each population was higher than the expected frequency. This result suggests a case of balanced polymorphism. The genotypes of the Cat locus were associated with marked differences in early mortality during the cultured period. The survival rate of each homozygote was lower than the mean survival rate in the population. The maintenance of stable polymorphism could be explained by differences in mortality among genotypes. Isocitrate dehydrogenase (IDH) was simultaneously examined as a control in the population structure. Homozygote excess at the Idh-1 locus was observed in some wild populations and an inbreeding structure was suggested.
All four carangid fish species (Trachurus japonicus, Caranx equula, C. sexfasciatus, and Alectis cilialis) studied here showed a diploid chromosome number of 48. The karyotype comprises all acrocentric pairs (nos. 1 to 24) in Alectis cilialis, but the largest chromosome pair (no. 1) changed into subtelocentrics in Caranx equula and C. sexfasciatus. In Trachurus japonicus the karyotype was different from the above three species by consisting of 15 biarmed chromosome pairs (nos. 1 to 15) and 9 acrocentric pairs (nos. 16 to 24). The sex chromosomes can not be identified in these 4 species. Based on these findings relation between the karyotype differentiation and species diversity of carangid fishes was discussed.
Histological examination of hybrid embryos developed by artificial insemination between female Norway rats (Rattus norvegicus, 2n=42) and male Asian type black rats (Rattus rattus flavipectus, 2n=42) was carried out with comparison between the hybrid and the control embryos which developed by artificial insemination between female and male Norway rats. Although the retardation of development of the hybrid embryo was observed, the endoderm and ectoderm were found well differentiated on the 7th and the 9th days. Until the 10th day after insemination, the hybrid embryos were clearly observed in the decidua although the development markedly delayed. The development of mesoderm was poor in this stage. On the 13th day the embryos appeared to be degenerated completely; only rudimental embryonic cells were observed in the decidua. Lethality of the hybrid embryos seemed to be due to the marked retardation of the development and differentiation.
Wheat cultures capable of plant regeneration were obtained from young embryos of Triticum aestivum cv. Chinese Spring and cv. Salmon, and were maintained by subculturing them every 30 to 40 days on RM-64 basal medium supplemented with 2.0mg/l of 2, 4-D. Fourteen-day old embryos were at the optimum age for the induction of cultures capable of plant regeneration. Histological observations showed many shoot apexes on the surface of these cultures. The cultures remained capable of differentiation for about 8 months, and complete plants were restored from them. Cultures from wheat embryos may be useful in mutant selection studies.
Karyotype analysis and cytophotometrical measurement of DNA content of nucleus were carried out in six species of Lycoris. Consistently with Inariyama (1951 a, b) the present study revealed that L. sprengeri (2n=22) and L. radiata pumila (2n=22) had 22 rod (acrocentric) chromosomes, L. aurea (2n=13) nine V-shaped (metacentric) chromosomes and four rods, L. albiflora (2n=17) five V's and twelve rods, L. squamigera (2n=27) six V's and 21 rods, while L. radiata (2n=33) 33 rods. There found a close proportionality between total chromosome length and relative DNA content of nucleus, and the more the number of V's is, the longer the total chromosome length and the more the DNA content of nucleus. On reference to cytological observations presented by Takemura (1961) and Koyama (1967), it is concluded that the V-shaped chromosome in Lycoris carries the extra segments proper to itself on both sides of the centromere.
A simplified apparatus for vertical acrylamide slab gel electrophoresis is described. This apparatus can be made very easily in laboratory. Examples of electrophoretic patterns obtained using this apparatus are given.