Eine asynaptische, röntgeninduzierte Pisum-Mutante wurde zytogenetisch untersucht. Als wesentliche Ergebnisse wurden erhalten: 1. Die Mutante beruht auf der Homozygotie eines rezessiven Gens. 2. Die Homologenpaarung im Pachytän unterbleibt. Als Folge werden keine Bivalente ausgebildet, was zu erheblichen Verteilungsanomalien führt. 3. Die Prophase ist verlängert; die PMZ-Entwicklung verläuft asynchron. 4. Es treten Chromosomenaberrationen auf (Brüche, geringe Spiralisation, stickiness, nucleic acid starvation). 5. Im Anschluß der Meiose erfolgt eine zusätzliche “Mitose”, nachdem die Kallose-Wände der Gonen abgebaut worden sind. 6. Die PMZ degenerieren. 7. Die Meiose-Störungen treten in der Mikro- und Makrosporogenese auf und bedingen Sterilität der mutierten Pflanzen.
The longest pair of autosomes was unequal in size in the majority of specimens of Spathosternum prasiniferum, collected from three different areas. Such an inequality was observed in oogonial and spermatogonial metaphases, spermatogonial anaphases, diplotene, diakinesis, I metaphase and second anaphases of meiosis in males. Analysis of the length of the unequal pair in gonial meta- and anaphases and second anaphases suggested a homogeneity between the differences and that the differences in absolute lengths are significant. Two specimens homozygous for the longer member of the unequal pair are recorded from each of the three areas.
The cytogenetic studies of triploid plant obtained from the progeny of tetraploid plants which were allowed to self-pollinate by preventing cross pollination, were undertaken. Abnormalities such as high frequency of univalents in diakinesis and metaphase with fragments in few cells, irregular anaphase I and II with micronuclei, few bridges with fragments and formation of polyads are quite frequently met with in the PMC's of this plant. The trivalent frequency is comparatively less and the chiasma frequency is 0.966. The occurrence of high frequency of univalents and fragments in the early stages of meiosis indicates the probable physiological imbalance in the PMC's which may results in the formation of weak chiasma leading to desynapsis and formation of chromosome fragments.
Nymphal Malpighian tubes of Triatoma infestans Klug have polyploid nuclei, as other insect groups. These nuclei, however, show heterochromatic bodies which have the number of replication steps not always in accordance with the euchromatin ones, in what they are similar to the Diptera. The nuclear volume does not follow the same increase in the DNA content per nucleus.
In the present investigation, the chromosome numbers for Lindenbergia indica (n=15 and 2n=30) and Mazus japonicus (n=20 and 2n=40) have been reported. The karyotype analysis revealed the presence of 4 and 8 satellited chromosomes respectively in their somatic complements. The two taxa under consideration show marked difference between them as regard the morphology of somatic chromosomes. On the basis of length, these chromosomes fall under 2 broad classes in both taxa but in L. indica they are either short or very short (9 morphological types) while in M. japonicus they are either long or medium-sized (12 morphological types). In general, the meiotic cycle is normal except showing a few cases of minor anomalies. In addition, multivalent formation takes place in M. japonicus. Secondary association of bivalents could be encountered in both taxa. In L. indica, as in some other genera under the family, the maximum association is in four groups indicating the basic number for the family. The presence of some extra-nuclear bodies in the pollen mother cells could be noted. These take bright stain with crystal violet but are Feulgen-negative. The karyotypes of four species worked out by the present authors, have been analysed. Moreover, the range of size variation in somatic chromosomes within the family have been compared and taxa possessing chromosome numbers in multiples of 5 (gametic) or 10 (somatic) have been enlisted. The phylogenetic significances of the presence of diverse nature of karyotypes, participation of unequal bivalents in units of secondary association and also the occurrence of both consistent and inconsistent numbers of chromosomes in members of the family have been discussed.
Various meiotic abnormalities were studied in PMC's of plants raised from seeds irradiated with various doses of gamma rays. The timing of onset of meiosis is highly disturbed in these plants. In Prophase chromosomes exhibit stickness and clumping and towards the end of prophase irrespective of the dosage, the cells contain fragments of chromosomes, univalents and disturbed bivalent association resulting in different configurations of chromosomes. The number of fragments and chromosome chain appearing as multivalents become more apparent towards the end of diakinesis. Chromosomes of different configurations including fragments are delayed ins Metaphase orientation and they are seen laying scattered or in groups in cytoplasm. The disturbed formation of spindle and the orientation of chromosomes in groups in metaphase are remarkably high in PMC's. In anaphase formation of micronuclei of different numbers and sizes, lagging chromeomes, fragrpents of chromosomes and chromatids, bridges with or without fragments are also very common. These abnormalities are carried forward and are also very commonly observed during second meiotic division. The frequency of occurrence of fragments is proportional to the dosage of gamma rays and also the presence of multivalents increases with the dose. These abnormalities seem to induce pollen sterility which is proportional to dose of gamma rays. This pollen sterility seems to be the cumulative result of various aberrant meiotic stages as well as physiological and genetic damages induced probably by the breakage of chromosomes through the formation of antimetabolic agents in these cells.
Fertilized Arbacia ova were incubated with H3-leucine from 30 minutes to 4 hours and thin sections (1 and 2μ) analyzed autoradiographically. The asters and MA incorporated H3-leucine at approximately the same rate than the whole cell. Puromycin and cycloheximide, depressed mitosis (94%). However, those cells that cleaved contained newly synthesized proteins.
1. In this report, a cytological study was made on six species of Spirogyra. Their chromosome number were as follows: Species name Chromosome number Spirogyra teodoresci 2 S. weberi 2 S. cylindrica 2 S. setiformis 4 S. peipingensis 4 S. fluviatilis 24 2. The chromosome number n=2 of Spirogyra teodoresci, S. weberi and S. cylindrica is the lowest chromosome number which is observed for the first time. The basic chromosome number of Spirogyra is thought to be x=2. 3. In three species of Spirogyra which have the basic chromosome number n=2, there is only one chloroplast band in one cell of gametophyte, and in species of polyploidy n=4 there are more chloroplast bands, i.e. two to six. In the two species having chromosome number n=4, the cell width of the gametophyte and the zygospore size are larger than that of the three species of n=2, but in S. fluviatilis (n=24) they are smaller than that of n=4.
Hybridization between Iberis amara varieties and I. pectinata was successful only when I. pectinata was the female parent. The seeds recovered from such crosses were much smaller than the control seeds from parents. The F1 hybrids were sterile but showed hybrid vigour and were morphologically intermediate between the two parents except in siliqua shape where the F1 hybrid resembled the maternal parent more closely. Very few seeds classified as small and large were obtained from F1 hybrid plants. The small seeds gave an F2 segregation of plants that resembled the parental and F1 hybrid types. Those F2 plants from large seeds were vigorous and fertile, and proved to be allotetraploids. Abundant seeds of three grades, small, intermediate, and large, were set by colchicine treated F1 hybrids. The C2 plants from small seeds showed a similar segregation as F2 plants from small seeds. Those from intermediate sized seeds were morphologically intermediate but varied considerably towards the I. amara parent. The C2 plants from large seeds were allotetraploids and were morphologically intermediates like F1 hybrids. They were vigorous and fertile. The allotetraploids were genetically isolated from the I. amara parent but not from I. pectinata. Cytological investigations in the parents, F1 and C1 populations revealed that the sterility of the F1 hybrids was largely of a chromosomal type and that the C1 plants were mixoploids. Although C1 plants produced triploid and tetraploid gametes, hexaploid and octoploid plants were not found in C2 populations.
1. Conspicuous morphological change was observed in rice pollen grains when they were left in the air after shedding. 2. Within a few minutes, a lot of vacuoles appeared around each pollen grain. Inclusion of the vacuoles was exuded from inside of pollen grains, but chemical analysis has not been carried out in the present study. 3. However, a rapid alteration in the physiological condition might have occurred to result in a decrease of germinability of pollen grains. And in part, this has been proved by TTC test. 4. Above described transformation of the pollen grains was characteristically occurred when they were shed sparsely on the slide glass. But when they were scattered densely, there were also observed a few pollen grains which kept the viability for longer time. 5. It was concluded that the rice pollen grains rapidly lost their viability by losing inner substances when they were left in the drought condition in the air. Further study on the physiological and metabolic disturbances in the course of losing viability, will throw light on the problem of longevity in rice pollen grains.
The arrangement of the chromomeres in relation to the chromosome axis in pre-pachytene chromosomes was studied with the light microscope in these plants: Vagaria parviflora, Fritillaria lanceolata, the garden tulip Mad. Lefeber and the hybrid lily Formobel. The fine structure of the leptotene chromosomes of some of these was also studied with the electron microscope. Evidence in support of the premise that chromomeres are formed eccentric to the axis of leptotene chromosomes, in order to segregate non-recombinational DNA from a pairing face, was obtained with the light microscope. The uncoiling of condensed parts of chromosomes, seen in pre-meiotic interphases and somatic nuclei of a lily, coincided with the onset of leptotene. Because of the alternation of chromomeres around the axis of the leptotene chromosomes, as a consequence of rotation, their eccentric alignment was difficult to confirm in thin sections with the electron microscope. The dense axial cores and less opaque chromomeral chromatin of leptotene chromosomes showed an equivalent staining behaviour with uranyl/lead ions and ethanolic phosphotungstic acid, thought to be largely specific for basic protein. No evidence was found of a close association of cores, indicative of pre-alignment of homologous chromosomes in pairs.
Fertile hybrids were produced between the two species M. longifolia (Linn.) Huds and M. rotundifolia L. which in nature are widely separated in their distribution. The hybrid inherited characters from both the parents. The speculated origin of M. spicata L. from the two parents has been disproved both cytologically and morphologically.
Chromosome pairing in the A0 generation of the amphiploids of Avena abyssinica (C.I. 2108)×A. strigosa (C.I. 7010) and in the A3 generation of the amphiploid of A. abyssinica (C.I. 7233)×A. strigosa (C.I. 2630) was analyzed. The average number of bivalents per pollen mother cell was higher in the A0 generation than in the A3 generation. Conversely, the average number of multivalents and univalents per cell was lower in the A0 than in the A3 generation. The difference in frequencies of kinds of pairing associations between A0 and A3 generations suggest that the A genomes of A. abyssinica and A. strigosa have differentiated. This differentiation, however, does not prevent the occasional pairing between A genome chromosomes of the diploid and tetraploid species. Such pairing and crossing over will eventually lead to formation of four completely homologous chromosomes in amphiploids of later generations. If we designate the A genome constitution of an autotetraploid as ADADADAD and a natural tetraploid as ATAT, then the genome constitution of the four homologous chromosomes in advanced generation amphiploids can be designated as AD-TAD-TAD-TAD-T A few multivalents and univalents were observed in PMCs of two derived tetraploid lines, 57-127 and 57-133, from synthetic 6X amphiploids. However, the most common association was 14 bivalents expected in a stable tetraploid line.
Polyploidy has been induced in four species of Trigonella viz. T. corniculata, T. hamosa, T. coerulea and T. cretica, all having 2n=16 by treating the seedlings with 0.2% aqueous solution of colchicine. Tetraploids of T. hamosa, T. coerulea and T. cretica exhibited morphological gigantism while tetraploid T. corniculata and mixoploid T. hamosa had smaller vegetative parts than the diploids. Frequency of multivalent formation has not been found to be related with chromosome length. Chromosome pairing and multivalent association seem to be under genetic control. Anaphase I irregularities increase with the increase of trivalents and univalents at metaphase I and pollen fertility has no correlation with the frequency of multivalents. Self-incompatibility is operative in three species both at diploid and tetraploid level. Both T. corniculata and T. hamosa seem to have played a role in the origin of T. polycerata.
By means of both light and electron microscopic studies, interphase nuclei in root tip cells of Crepis capillari s are classified into five classes (class 1, 2, 3, 4 and class 5) according to their characteristic morphological differences. It was able to establish a correlated relationship between the topographical status of the five interphase nuclei and their corresponding states at different periods in the interphase. This is achieved by the use of an improved electron microscopic autoradiography. The results obtained have indicated that the nuclei of class 1 type correspond to the nuclei at the G1 period, and those belong to class 2 and 3 types, correspond respectively to the nuclei at the S period and G2 period, and the nuclei belong to classes 4 and 5 are presumed to correspond to nuclei which are going into a process of further differentiation, not going into the subsequent mitosis anymore.
Sternbergia fischeriana, a spring flowering bulbous annual, is the only species of the genus cultivated in Kashmir. Somatic complement of this species consists of 4 submedian and 18 subterminal chromosomes. The karyotype resembles that of S. lutea, an autumn flowering species worked out by Battaglia (1949). Though the species is heterozygous for three interchanges and a paracentric inversion, it has not as yet developed a balanced lethal system to maintain this heterozygosity. Vegetative reproduction, however, comes to its rescue and enables it not only to overcome the bottleneck of total sterility but also to conserve hybridity.
Terminal uptake of 3H-thymidine and autoradiography were employed to study the late replication pattern of chromosomes from three day old embryos of the domestic fowl, Gallus domesticus. In the male both Z chromosomes replicated synchronously while the W chromosome of the female replicated asynchronously relative to the Z chromosome. Contrary to previous studies, the microchromosomes appeared to replicate during the same time as the macrochromosomes. The data indicated that the pattern of replication was not necessarily the same for all cells and that the mitotic cycle differed in cells of various tissues. The inconsistencies in replication pattern and mitotic cycle are probably a reflection of differentiation in the embryo. The behavior of the microchromosomes indicates they are true chromosomes. Silver grains were distributed in a nonrandom fashion over interphase nuclei, indicating some degree of chromosome organization exists during the S period.
The chromosome constitution of 9 primary hepatomas induced by 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) in rats was investigated with the aid of tissue culture methods. Among them, 4 cases were found to have a chromosome mode in the diploid range, 1 case showed a hypotriploid mode, and the remaining 4 cases had a mode in the hypotetraploid range; though every hepatoma had a wide varieiy of distribution of chromosome numbers. A substantial number of the tumors contained several types of abnormal chromosomes; however, their karyotypes were different from tumor to tumor. In contrast, 3 tumors with a diploid mode were found to possess stem cells with 42 chromosomes without any detectable structural modifications. The significance of the presence of such diploid cells in tumors is discussed.
In three species of jumping spider belonging to the genus Phidippus, we found the male underwent normal spermatogenesis. The diploid complement of the males of regius, audax and johnsoni is 22 and all species have an X1O+X2O type of sex-determining mechanism. The smallest elements in the complement represent the two X-chromosomes, which are peripherally situated at the first meiotic metaphase and during separation precede the autosomal bivalents to one of the poles. The two types of spermatids thus formed contain 10 and 10+X1O+X2O chromosomes respectively.
The three phyla investigated to determine the presence or absence of sex specific chromatin masses were the Arthropoda, Annelida and Mollusca. The arthropods were represented by members of the classes Insecta, Crustaceae, Arachnida, Chilopoda and Diplopoda; the molluscs by a member of the class Pelecypoda; and the annelids by a member of the class Polychaeta. The Feulgen technique and two different techniques using Biebrich scarlet and fast green FCF were used to demonstrate sex distinctive chromatin in tissue sections. No nuclear sexual dimorphism was evident in the interphase nuclei of somatic cells in the different genera of molluscs or annelids examined. In the Arthropoda only one organism, the male Phlocus phalangioides, in the three genera which represented the arachnids had a sex distinctive chromatin mass. Of the crustaceans examined, sex distinctive masses were seen only in somatic cell nuclei of the male Cambarus affinis and the male Cancer sp. No nuclear dimorphism was noted in the genera which represented the Chilopoda and Diplopoda or in nine of the eleven insect orders studied. In the ten genera of the order Lepidoptera examined, the interphase nuclei of adult and larval females had a distinct chromatin mass which was not seen in male nuclei. One member of the order Hemiptera, the immature and mature male Oncopeltus fasciatus, demonstrated a sex distinctive chromatin mass.