An apomictic mutant for sticky chromosomes in the fern Ceratopteris

1977 ◽  
Vol 55 (16) ◽  
pp. 2186-2195 ◽  
Author(s):  
Leslie G. Hickok
Keyword(s):  
Meiotic Division ◽  
Mitotic Division ◽  
Triploid Hybrid ◽  
Restitution Nucleus ◽  
Chromosome Stickiness

A meiotic mutant has been derived from a triploid hybrid of the fern genus Ceratopteris. The mutant behavior involves chromosome stickiness that is regularly observed during both meiotic divisions. Chromosome stickiness is also infrequently observed during mitotic division. In addition, the first meiotic division frequently fails and results in the formation of a restitution nucleus. A single second meiotic division follows restitution and results in the production of a dyad of unreduced spores. Viable unreduced spores germinate to produce gametophytes containing the sporophytic number of chromosomes. Spermatozoids produced by the gametophytes are non-functional. However, sporophytes regularly develop apogamously from the gametophytes. Because meiotic reduction and syngamy are absent, the mutants are, reproductively, obligate apomicts.

scholarly journals Assembly and Positioning of the Oocyte Meiotic Spindle

2018 ◽  
Vol 34 (1) ◽  
pp. 381-403 ◽  
Author(s):  
Binyam Mogessie ◽  
Kathleen Scheffler ◽  
Melina Schuh
Keyword(s):  
Menstrual Cycle ◽  
Recent Work ◽  
Meiotic Division ◽  
Polar Body ◽  
Mitotic Division ◽  
Model System ◽  
Small Cell ◽  
Meiotic Spindle ◽  
Polar Body Extrusion ◽  
Shed Light

Fertilizable eggs develop from diploid precursor cells termed oocytes. Once every menstrual cycle, an oocyte matures into a fertilizable egg in the ovary. To this end, the oocyte eliminates half of its chromosomes into a small cell termed a polar body. The egg is then released into the Fallopian tube, where it can be fertilized. Upon fertilization, the egg completes the second meiotic division, and the mitotic division of the embryo starts. This review highlights recent work that has shed light on the cytoskeletal structures that drive the meiotic divisions of the oocyte in mammals. In particular, we focus on how mammalian oocytes assemble a microtubule spindle in the absence of centrosomes, how they position the spindle in preparation for polar body extrusion, and how the spindle segregates the chromosomes. We primarily focus on mouse oocytes as a model system but also highlight recent insights from human oocytes.

Fertility and meiotic mechanisms of hybrids between chromosome autoduplication tetraploid wheats and Aegilops species

Genome ◽  
1992 ◽  
Vol 35 (3) ◽  
pp. 379-384 ◽  
Author(s):  
Shujun Xu ◽  
Yushen Dong
Keyword(s):  
Meiotic Division ◽  
Seed Set ◽  
Tetraploid Wheat ◽  
Unreduced Gametes ◽  
Root Tip ◽  
Aegilops Species ◽  
Chromosome Counts ◽  
Restitution Nucleus ◽  
New Knowledge ◽  
Anucleate Cell

During the production of Triticum-Aegilops amphidiploids, it was observed that some F1 hybrids between Triticum ssp. and Aegilops ssp. were self-fertile, with seed set ranging from 0.97 to 39.72%. Seeds from fertile F1's were spontaneous amphidiploids, as determined by root-tip chromosome counts. The present study revealed that the autoduplication of chromosomes in these F1's was caused by the tetraploid wheat parents T. persicum PS5 and T. durum DR147. Detailed meiotic studies of T. persicum PS5 crossed with Ae. squarrosa showed that during meiosis, there were two ways by which unreduced gametes could be formed: first, some of the PMCs omitted the first meiotic division and only underwent the second meiotic division and second, first division restitution with premature cytokinesis, which resulted in an asymmetrical dyad composed of one anucleate cell and one cell with a restitution nucleus. This cell produced two unreduced microspores by a normal second division. The use of this new knowledge has resulted in the production of numerous spontaneous amphiploids of T. persicum crossed with Ae. squarrosa, Ae. speltoides, Ae. umbellulata, Ae. comosa, Ae. ovata, Ae. ventricosa, Ae. crassa, and Ae. triuncialis. Many of these have been produced for the first time.Key words: Triticum, Aegilops, chromosome autoduplication, unreduced gametes, amphidiploids.

Activity patterns of nucleolar organizer region during spermatogenesis of different curimatid species (Characiformes: Curimatidae)

Genome ◽  
2014 ◽  
Vol 57 (2) ◽  
pp. 119-124 ◽  
Author(s):  
Tatiane R. Sampaio ◽  
Larissa B. Pires ◽  
Renata da Rosa ◽  
Ana Lúcia Dias
Keyword(s):  
Silver Nitrate ◽  
Meiotic Division ◽  
Activity Patterns ◽  
Organizer Region ◽  
Nucleolar Organizer Region ◽  
Nucleolar Organizer ◽  
Mitotic Division ◽  
Nucleolar Organizer Regions ◽  
Rdna Transcription ◽  
Fluorochrome Staining

The nucleolus is an important nuclear structure where transcription of ribosomal DNA (rDNA) takes place. During mitotic division, the nucleolus passes through different processes that inactivate rDNA transcription; in meiosis, its reassembly takes place during telophase II. The objective of this study was to identify the activity patterns and localization of nucleolar organizer regions (NORs) during meiotic division in fish species of the family Curimatidae. For this analysis, the meiotic division in five curimatid species was studied using silver nitrate impregnation, fluorescent in situ hybridization (FISH), and base-specific fluorochrome staining. Silver nitrate staining indicated the presence of a nucleolus in interphase nuclei, one chromosome pair in the spermatogonial metaphases, and one bivalent at the pachytene stage. No Ag-NORs were identified for cells at the diplotene, diakinesis, metaphase I, or metaphase II stages; however, FISH confirmed the presence of Ag-NORs in the nuclei, in spermatogonia, and at the pachytene phase. FISH identified this region during the other stages of meiosis, as did fluorochrome CMA3 staining, which revealed fluorescent marks corresponding to NORs during all stages of meiosis analyzed. The gene activity and localization of this ribosomal sequence during the different stages involved will also be discussed.

scholarly journals Ultrastructure of Nuclear Division in Paramecium Aurelia III. Meiosis in the Micronucleus During Conjugation

1972 ◽  
Vol 25 (4) ◽  
pp. 775 ◽  
Author(s):  
I Stevenson
Keyword(s):  
Meiotic Division ◽  
Nuclear Division ◽  
Mitotic Division ◽  
Pair Formation ◽  
The Other ◽  
Condensed Chromatin ◽  
Synaptinemal Complex ◽  
The Core ◽  
Female Pronucleus ◽  
The One

Ultrastructural features of micronuclear meiosis occurring during conjugation of the ciliate P. aurelia are described. Following pair formation the micronuclei enter prophase. The core of condensed chromatin in the micronucleus fragments, and almost the whole nucleus becomes filled with coiled and twisted chromatin elements. After about 1� 5 hr of pairing regions of condensed chromatin appear linked into strands 1-2 p;m long. Somewhat later, ill-defined, synaptinemal, complex-like material lies between paired masses of chromatin. Only a few synaptinemal complex-like structures can be seen in the nucleus. A short while later, synaptinemal complex-like material may be seen free in the nucleoplasm. After about 2�5 hr of pairing, the micronucleus expands into the crescent stage. Microtubules appear in the nucleus, which expands rapidly to a length of about 20 /Lm, usually oriented along the long axis of the cell. Concurrently with expansion the chromatin becomes diffuse and spreads along the length of the nucleus. This stage probably corresponds to diplotene. The nuoleus then shrinks, miorotubules reappear, and metaphase of the first meiotic division oocurs. A large number of chromosomes, with indistinct kinetochores, can be seen. At telophase the nucleus is 15-20 /Lm long and dumbbell-shaped. It breaks into two parts, there being no separation spindle, in contrast to mioronuclear mitosis. The seoond meiotic division occurs immediately. Ultrastructurally it resembles the first with respeot to metaphase, anaphase, and telophase. Since P. aurelia has two micronuclei, there are eight haploid meiotic products. The one nearest the paroral cone survives and the other seven disintegrate and are resorbed. The remaining nucleus undergoes a modified mitotic division. One of the two final produots becomes a stationary ("female") pronucleus, while the other becomes a migratory ("male") pronuoleus. Male pronuclei are exchanged aoross the fused paroral oone regions of the partners. The male pronucleus contains microtubules during its migration. After fusion to produce the synkaryon, the conjugants separate.

Gametogenesis and fertilization in Dirofilaria immitis (Nematoda: Filarioidea)

Parasitology ◽  
1986 ◽  
Vol 92 (1) ◽  
pp. 181-197 ◽  
Author(s):  
C. J. Delves ◽  
R. E. Howells ◽  
R. J. Post
Keyword(s):  
Meiotic Division ◽  
Dirofilaria Immitis ◽  
Chromosome Complement ◽  
Male Gamete ◽  
Mitotic Division ◽  
Hormonal Control ◽  
Polar Bodies ◽  
Primary Oocyte ◽  
Chromatin Material

SUMMARYGametogenesis in Dirofilaria immitis has been studied principally by means of the aceto-orcein chromosomal squash technique, but with additional ultrastructural observations. A terminal germinative zone, in which a continuous and rapid division of germ cells occurs, has been identified in the gonoduct of both male and female worms. Approximately 20% of cells within these germinative zones were in arrested mitotic division following the incubation in vitro of excised gonads in 0·01% colchicine for 4 h. All primary spermatocytes within a 1–2 cm length of the testis proximal to the germinative zone were at the prophase of the 1st meiotic division. In the corresponding region of the ovary, the primary oocytes were similarly at the prophase of the 1st meiotic division in 75% of female worms examined but in the remaining 25% all primary oocytes possessed markedly less condensed, probably interphase nuclei. A possible hormonal control of the cyclical development of primary oocytes, but not primary spermatocytes in D. immitis is suggested. In most of the remaining length of the gonoducts beyond this region of cells at meiotic prophase, the chromatin material of both primary spermatocytes and oocytes is decondensed. Recondensation of chromosomes in the spermatocytes is observed just prior to entry into the seminal vesicle, where meiosis I is completed and meiosis II takes place. In the primary oocyte, completion of meiosis only occurs after fertilization within the seminal receptacle by an entire male gamete. Following the 2 meiotic divisions in the oocyte and subsequent extrusion of the 2 polar bodies, the haploid chromosome complement of the female unites with that of the male, re-establishing the diploid number of the zygote (2n = 10). Male chromosomes within the oocyte remain visible throughout late oogenesis and fusion occurs without the formation of pronuclei.

Ultrastructure of primary spermatocyte in fish (Tilapia: Oreochromis niloticus): The synaptonemal complex

1986 ◽  
Vol 44 ◽  
pp. 288-289
Author(s):  
T. Guha ◽  
A. Q. Siddiqui ◽  
P. F. Prentis
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Synaptonemal Complex ◽  
Oreochromis Niloticus ◽  
Short Communication ◽  
Primary Spermatocyte ◽  
Mitotic Division ◽  
Meiotic Cell ◽  
Electron Microscope Level ◽  
Homologous Chromosomes

The Primary Spermatocytes represent a stage in spermatogenesis when the first meiotic cell division occurs. They are derived from Spermatogonium or Stem cell through mitotic division. At the zygotene phase of meiotic prophase the Synaptonemal complex appears in these cells in the space between the paired homologous chromosomes. Spermatogenesis and sperm structure in fish have been studied at the electron microscope level in a few species? However, no work has yet been reported on ultrastructure of tilapia, O. niloticus, spermatozoa and spermatogenetic process. In this short communication we are reporting the Ultrastructure of Primary Spermatocytes in tilapia, O. niloticus, and the fine structure of synaptonemal complexes seen in the spermatocyte nuclei.

scholarly journals ISOLATION OF SPO12–1 AND SPO13–1 FROM A NATURAL VARIANT OF YEAST THAT UNDERGOES A SINGLE MEIOTIC DIVISION

Genetics ◽  
1980 ◽  
Vol 96 (3) ◽  
pp. 567-588 ◽  
Author(s):  
Sue Klapholz ◽  
Rochelle Easton Esposito
Keyword(s):  
Genetic Analysis ◽  
Meiotic Division ◽  
Parental Strain ◽  
Nuclear Division ◽  
Nuclear Genes ◽  
Vegetative Cells ◽  
Total Level ◽  
Natural Variant ◽  
Chromosome Viii

ABSTRACT ATCC4117 is a strain of S. cerevisiae that undergoes a single nuclear division during sporulation to produce asci containing two diploid ascospores (Grewal and Miller 1972). All clones derived from these spores are sporulation-capable and, like the parental strain, form two-spored asci. In this paper, we describe the genetic analysis of ATCC4117. In tetraploid hybrids of vegetative cells of the ATCC4117 diploid and a/a or α/α diploids, the production of two-spored asci is recessive. From these tetraploids, we have isolated two recessive alleles, designated spo12–1 and spo13–1, each of which alone results in the production of asci with two diploid or near-diploid spores. These alleles are unlinked and segregate as single nuclear genes. spo12–1 is approximately 22 cM from its centromere; spo13–1 has been localized to within 1 cM of arg4 on chromosome VIII. This analysis also revealed that ATCC4117 carries a diploidization gene allelic to or closely linked to HO, modifiers that reduce the number of haploid spores per ascus and alleles affecting the total level of sporulation.

scholarly journals A Screen for Genes Involved in the Anaphase Proteolytic Pathway Identifies tsm1+, a Novel Schizosaccharomyces pombe Gene Important for Microtubule Integrity

Genetics ◽  
1998 ◽  
Vol 149 (3) ◽  
pp. 1251-1264
Author(s):  
Ekaterina L Grishchuk ◽  
James L Howe ◽  
J Richard McIntosh
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Nuclear Division ◽  
Mitotic Division ◽  
Temperature Sensitive ◽  
Permissive Temperature ◽  
Anaphase Promoting Complex ◽  
Chloromethyl Ketone ◽  
Proteolytic Pathway ◽  
Functional Involvement ◽  
Spindle Elongation

Abstract The growth of several mitotic mutants of Schizosaccharomyces pombe, including nuc2-663, is inhibited by the protease inhibitor N-Tosyl-L-Phenylalanine Chloromethyl Ketone (TPCK). Because nuc2+ encodes a presumptive component of the Anaphase Promoting Complex, which is required for the ubiquitin-dependent proteolysis of certain proteins during exit from mitosis, we have used sensitivity to TPCK as a criterion by which to search for novel S. pombe mutants defective in the anaphase-promoting pathway. In a genetic screen for temperature-sensitive mitotic mutants that were also sensitive to TPCK at a permissive temperature, we isolated three tsm (TPCK-sensitive mitotic) strains. Two of these are alleles of cut1+, but tsm1-512 maps to a novel genetic location. The tsm1-512 mutation leads to delayed nuclear division at restrictive temperatures, apparently as a result of an impaired ability to form a metaphase spindle. After shift of early G2 cells to 36°, tsm1-512 arrests transiently in the second mitotic division and then exits mitosis, as judged by spindle elongation and septation. The chromosomes, however, often fail to segregate properly. Genetic interactions between tsm1-512 and components of the anaphase proteolytic pathway suggest a functional involvement of the Tsm1 protein in this pathway.

scholarly journals GAMMA RAY - INDUCED MITOTIC ABNORMALITIES IN Helianthus annuus L. VARIETY EKIZ 1 / LOS RAYOS DE GAMMA CAUSA ANORMALIDADES MITOTICAS EN Helianthus annuus L. VARIEDAD DE EKIZ 1 / LES ANORMALITÉS MITOTIQUES CHARGÉÉS DES RAYONS GAMMA

Helia ◽  
2001 ◽  
Vol 24 (35) ◽  
pp. 39-46
Author(s):  
Orhan Arslan ◽  
Şenol Bal ◽  
Nilgün Venice ◽  
Semra Mirici
Keyword(s):  
Helianthus Annuus ◽  
Mitotic Index ◽  
Gamma Rays ◽  
Metaphase Chromosome ◽  
Gamma Ray ◽  
Dose Increase ◽  
Helianthus Annuus L ◽  
Mitotic Abnormalities ◽  
Chromosome Stickiness

SUMMARYIn this study, mitotic effects of gamma rays on Ekiz 1 variety belonging to Helianthus annuus L. (2n= 34) in the M0 (first irradiated seeds), M1 and M2 generations have been investigated. Seeds (M0) were irradiated with gamma rays at 10, 20, 30, 40 and 50 kR doses. Percentage of total abnormalities in the M0, M1 and M2 generations increased parallel to the increasing dose of radiation. These abnormalites have been observed as C-metaphase, chromosome stickiness, laggards and bridges with or without fragment. Mitotic index (M.I.) in the M0, M1 and M2 generations has decreased parallel to the dose increase. When the generations are compared, both the amounts of decrease in mitotic index and in the percentage of mitotic abnormalities were mostly observed in M0.

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