scholarly journals A ZIP1 Separation-of-Function Allele Reveals that Meiotic Centromere Pairing Drives Meiotic Segregation of Achiasmate Chromosomes in Budding Yeast

2018 ◽  
Author(s):  
Emily L. Kurdzo ◽  
Hoa H Chuong ◽  
Dean S. Dawson
Keyword(s):  
Chromosome Number ◽  
Single Unit ◽  
Genetic Recombination ◽  
Budding Yeast ◽  
Homologous Chromosomes ◽  
Normal Number ◽  
Relationship Of ◽  
Distinct Features ◽  
The Relationship ◽  
Meiosis I

ABSTRACTIn meiosis I, homologous chromosomes segregate away from each other - the first of two rounds of chromosome segregation that allow the formation of haploid gametes. In prophase I, homologous partners become joined along their length by the synaptonemal complex (SC) and crossovers form between the homologs to generate links called chiasmata. The chiasmata allow the homologs to act as a single unit, called a bivalent, as the chromosomes attach to the microtubules that will ultimately pull them away from each other at anaphase I. Recent studies, in several organisms, have shown that when the SC disassembles at the end of prophase, residual SC proteins remain at the homologous centromeres providing an additional link between the homologs. In budding yeast, this centromere pairing is correlated with improved segregation of the paired partners in anaphase. However, the causal relationship of prophase centromere pairing and subsequent disjunction in anaphase has been difficult to demonstrate as has been the relationship between SC assembly and the assembly of the centromere pairing apparatus. Here, a series of in-frame deletion mutants of the SC component Zip1 were used to address these questions. The identification of separation-of-function alleles that disrupt centromere pairing, but not SC assembly, have made it possible to demonstrate that centromere pairing and SC assembly have mechanistically distinct features and that prophase centromere pairing function of Zip1 drives disjunction of the paired partners in anaphase I.AUTHOR SUMMARYThe generation of gametes requires the completion of a specialized cell división called meiosis. This division is unique in that it produces cells (gametes) with half the normal number of chromosomes (such that when two gametes fuse the normal chromosome number is restored). Chromosome number is reduced in meiosis by following a single round of chromosome duplication with two rounds of segregation. In the first round, meiosis I, homologous chromosomes first pair with each other, then attach to cellular cables, called microtubules, that pull them to opposite sides of the cell. It has long been known that the homologous partners become linked to each other by genetic recombination in a way that helps them behave as a single unit when they attach to the microtubules that will ultimately pull them apart. Recently, it was shown, in budding yeast and other organisms, that homologous partners can also pair at their centromeres. Here we show that this centromere pairing also contributes to proper segregation of the partners away from each other at meiosis I, and demonstrate that one protein involved in this process is able to participate in multiple mechanisms that help homologous chromosomes to pair with each other before being segregated in meiosis I.

3.—The Cytology of the Parthenogenetic Australian Weevil Listroderes costirostris Schönh

1973 ◽  
Vol 69 (3) ◽  
pp. 71-89 ◽  
Author(s):  
Ann R. Sanderson
Keyword(s):  
Body Size ◽  
Chromosome Number ◽  
Polar Nucleus ◽  
Low Fertility ◽  
Arrested Development ◽  
Relationship Of ◽  
Bouquet Stage ◽  
The Relationship

SynopsisKaryograms prepared from ovarian and blastoderm cells of the parthenogenetic Australian Brown Vegetable Weevil demonstrate a consistent triploid condition with 30 chromosomes which can be grouped into 10 sets of homologues. Meiosis is replaced by a single mitotic-like division in which 30 univalent chromosomes, each composed of two chromatids, divide equationally between an ootid nucleus and a single polar nucleus. Prior to the differentiation of the oocytes a peculiar bouquet stage occurs in the cells of the end chamber of each ovariole, but the significance of this phase is not known. Arrested development in eggs from individuals of low fertility is investigated and the relationship of body size and chromosome number is discussed.

COCCIDIOIDES IMMITIS: CYTOLOGICAL STUDY ON THE FORMATION OF THE ARTHROSPORES

1969 ◽  
Vol 11 (1) ◽  
pp. 43-53 ◽  
Author(s):  
Kyung Joo Kwon-Ciiung
Keyword(s):  
Chromosome Number ◽  
Nuclear Division ◽  
Cytological Study ◽  
Ring Stage ◽  
Coccidioides Immitis ◽  
Active Growth ◽  
Spindle Apparatus ◽  
Relationship Of ◽  
The Relationship

Somatic nuclear division and the manner of arthrospore formation in saprophytic phase of Coccidioides immitis have been studied. Two distinct nuclear cycles, one occurring during the active growth in young hyphae and another occurring in old thin hyphae or during arthrospore formation, were observed. The first cycle consisted of several stages starting from round resting nuclei → ring stage → V stage → and filaments which divide longitudinally. The two daughter nuclear filaments reorganize into round nuclei. The second cycle is more simple than the first. The round resting nuclei become elongated and constricted at the middle, dividing vertically. The chromosome number appears to be 3. The metaphase plares or spindle apparatus were not seen.The fertile hyphae develop septa not basipetally but synchronously. Alternate cells, after being thus delimited, increase in size and in thickness of wall becoming spores while the intervening cells gradually lose cytoplasm. The nuclei remain, without cytoplasm, in the intervening cells until the adjacent spores are completely matured. The spores are released by fragmentation of the walls of the sterile segments. The relationship of C. immitis to the members of Gymnoascaceae has been discussed.

scholarly journals Shugoshin protects centromere pairing and promotes segregation of non-exchange partner chromosomes in meiosis

2018 ◽  
Author(s):  
Luciana Previato de Almeida ◽  
Jared M. Evatt ◽  
Hoa H. Chuong ◽  
Emily L. Kurdzo ◽  
Craig A. Eyster ◽  
...  
Keyword(s):  
Synaptonemal Complex ◽  
Chromosome Segregation ◽  
Meiotic Prophase ◽  
Single Unit ◽  
Meiotic Chromosome ◽  
Model Systems ◽  
Meiotic Spindle ◽  
Homologous Chromosomes ◽  
Meiosis I

ABSTRACTFaithful chromosome segregation during meiosis I depends upon the formation of connections between homologous chromosomes. Crossovers between homologs connect the partners allowing them to attach to the meiotic spindle as a unit, such that they migrate away from one another at anaphase I. Homologous partners also become connected by pairing of their centromeres in meiotic prophase. This centromere pairing can promote proper segregation at anaphase I of partners that have failed to become joined by a crossover. Centromere pairing is mediated by synaptonemal complex (SC) proteins that persist at the centromere when the SC disassembles. Here, using mouse spermatocyte and yeast model systems, we tested the role of shugoshin in promoting meiotic centromere pairing by protecting centromeric synaptonemal components from disassembly. The results show that shugoshin protects centromeric SC in meiotic prophase and, in anaphase, promotes the proper segregation of partner chromosomes that are not linked by a crossover.SIGNIFICANCEMeiotic crossovers form a connection between homologous chromosomes that allows them to attach to the spindle as a single unit in meiosis I. In humans, failures in this process are a leading cause of aneuploidy. A recently described process, called centromere pairing, can also help connect meiotic chromosome partners in meiosis. Homologous chromosomes become tightly joined by a structure called the synaptonemal complex (SC) in meiotic prophase. After the SC disassembles, persisting SC proteins at the centromeres mediate their pairing. Here, studies in mouse spermatocytes and yeast are used to show that the shugoshin protein helps SC components persist at centromeres and helps centromere pairing promote the proper segregation of yeast chromosomes that fail to become tethered by crossovers.

scholarly journals Integral Values in Madrasah: to Foster Community Trust in Education

2020 ◽  
Vol 5 (2) ◽  
pp. 160
Author(s):  
M Sayyidul Abrori ◽  
Moh. Solikul Hadi
Keyword(s):  
Symbolic Interactionism ◽  
General Public ◽  
Single Unit ◽  
Formal Education ◽  
Public Trust ◽  
Education Level ◽  
Community Trust ◽  
Relationship Of ◽  
The Relationship ◽  
Basic Level

This article aims to illustrate the reality of the relationship between public trust in madrasas. The pattern of the relationship examined is not only limited to individual students, guardians of students or managers of madrasas, but to other people such as their families and society in general. This is done to understand the trust that was initially built only at the level of individual students or guardians of students or madrasah managers also occur at the level of the general public until a sociological trust is formed. In general, the community does not know and understand clearly what is a madrasa and what is a school. Madrasahs are often understood as non-formal education for madrasah diniyah which implements learning every evening.The discussion of madrasas in this paper is a formal education madrasa under the auspices of the Ministry of Religion in the field of Madrasah Education whose education level starts from the most basic level, namely RaudhatulAthfal (RA), Madrasah Ibtidaiyah (MI), Madrasah Tsanawiyah (MTs) to Madrasah Aliyah (MA) or Madrasah Aliyah Kejuruan (MAK). Where the level above is a single unit that is mutually sustainable. The results showed that the relationship of public trust is not always based on consideration of rational economic transactional but also based on moral rationality and religiosity. This is where trust develops between students or guardians of students and madrasah managers. From the perspective of symbolic interactionism, the behavior of students or guardians of students and madrasah managers reflects the meaning of worship and reinforces their relationship of trust with their religiosity.Artikel ini bertujuan untuk menggambarkan realitas hubungan antara kepercayaan publik terhadap madrasah. Pola hubungan yang diteliti tidak hanya terbatas pada siswa perorangan, wali murid atau pengelola madrasah, tetapi juga bagi orang lain seperti keluarga dan masyarakat pada umumnya. Hal ini dilakukan untuk memahami kepercayaan yang pada awalnya dibangun hanya pada tingkat siswa perorangan atau wali siswa atau manajer madrasah juga terjadi pada tingkat masyarakat umum sampai kepercayaan sosiologis terbentuk. Secara umum, masyarakat tidak tahu dan mengerti dengan jelas apa itu madrasah dan apa itu sekolah. Madrasah sering dipahami sebagai pendidikan non-formal untuk madrasah diniyah yang menerapkan pembelajaran setiap malam. Pembahasan madrasah dalam tulisan ini adalah madrasah pendidikan formal di bawah naungan Kementerian Agama di bidang Pendidikan Madrasah yang tingkat pendidikannya dimulai dari jenjang paling dasar, yaitu Raudhatul Athfal (RA), Madrasah Ibtidaiyah (MI), Madrasah Tsanawiyah (MTs) ke Madrasah Aliyah (MA) atau Madrasah Aliyah Kejuruan (MAK). Dimana level di atas adalah satu unit yang saling berkelanjutan. Hasil penelitian menunjukkan bahwa hubungan kepercayaan publik tidak selalu didasarkan pada pertimbangan transaksional ekonomi rasional tetapi juga didasarkan pada rasionalitas moral dan religiusitas. Di sinilah kepercayaan berkembang antara siswa atau wali siswa dan pengelola madrasah. Dari perspektif interaksionisme simbolik, perilaku siswa atau wali siswa dan manajer madrasah mencerminkan makna ibadah dan memperkuat hubungan kepercayaan mereka dengan agama mereka.

SARS-CoV-2: Evaluation and Evolution

Coronaviruses ◽  
2021 ◽  
Vol 02 ◽  
Author(s):  
Loay Bedda ◽  
Fayrouz Mahmoud ◽  
Radwa Elkhateib ◽  
Alyaa Dawoud ◽  
Hassan Gamal ◽  
...  
Keyword(s):  
Life Cycle ◽  
Genetic Recombination ◽  
Virus Evolution ◽  
High Morbidity ◽  
Nucleotide Polymorphisms ◽  
Single Nucleotide ◽  
S Protein ◽  
Viral Genomes ◽  
Relationship Of ◽  
The Relationship

: The emerging new COVID 2019 pandemic, which started in 2019 in China (Wuhan) and is caused by SARS-CoV-2, raises critical concerns due to high morbidity and mortality. Given a large number of infected individuals and the fact that the number continues to rise, it's possible that the virus has multiple variants, some of which are more pathogenic than others.Besides, the virus is suspected of various evolutionary pathways since SARS-CoV-2 belongs to the RNA viruses’ family, which is characterized by a high mutation rate. Additionally, it is crucial to understand the life cycle of the virus to be able to urge antiviral studies. Genotyping studies about viruses are also important in order to understand the transmission and evolution of the virus. The genome of SARS-CoV-2 has a furin-like cleavage site in its S protein that may affect its pathogenicity. It was found that insertions and deletions in S protein have an impact on the transmission and fusion of the virus. The single nucleotide polymorphisms (SNP) genotypes are used to track the relationship of virus isolates. Sequence alignment revealed the presence of hundreds of inter-host mutations during person-to-person transmission. Furthermore, genetic recombination provided a second mechanism for virus evolution. In this review, we highlight the life cycle of the virus and methods of virus evolution caused by mutations or recombination of viral genomes.

Developmental regulation of SPO13, a gene required for separation of homologous chromosomes at meiosis I

1987 ◽  
Vol 7 (4) ◽  
pp. 1425-1435
Author(s):  
H T Wang ◽  
S Frackman ◽  
J Kowalisyn ◽  
R E Esposito ◽  
R Elder
Keyword(s):  
Genetic Recombination ◽  
Developmental Regulation ◽  
Maximum Level ◽  
Mitotic Cell ◽  
Sporulation Medium ◽  
Developmentally Regulated ◽  
Type Locus ◽  
Homologous Chromosomes ◽  
Diploid Cells ◽  
Meiosis I

Previous studies have demonstrated that the SPO13 gene is required for chromosome separation during meiosis I in Saccharomyces cerevisiae. In the presence of the spo13-1 nonsense mutation, MATa/MAT alpha diploid cells complete a number of events typical of meiosis I including premeiotic DNA synthesis, genetic recombination, and spindle formation. Disjunction of homologous chromosomes, however, fails to occur. Instead, cells proceed through a single meiosis II-like division and form two diploid spores. In this paper, we report the cloning of this essential meiotic gene and an analysis of its transcription during vegetative growth and sporulation. Disruptions of SPO13 in haploid and diploid cells show that it is dispensible for mitotic cell division. Diploids homozygous for the disruptions behave similarly to spo13-1 mutants; they sporulate at wild-type levels and produce two-spored asci. The DNA region complementing spo13-1 encodes two overlapping transcripts, which have the same 3' end but different 5' ends. The major transcript is 400 bases shorter than the larger, less abundant one. The shorter RNA is sufficient to complement the spo13-1 mutation. While both transcripts are undetectable or just barely detectable in vegetative cultures, they each undergo a greater than 70-fold induction early during sporulation, reaching a maximum level about the time of the first meiotic division. In synchronously sporulating populations, the transcripts nearly disappear before the completion of ascus formation. Nonsporulating cells homozygous for the mating-type locus show a small increase in abundance (less than 5% of the increase in sporulating cells) of both transcripts in sporulation medium. These results indicate that expression of the SPO13 gene is developmentally regulated and starvation alone, independent of the genotype at MAT, can trigger initial induction.

GENOME RELATIONS BETWEEN PASPALUM CONSPERSUM AND TWO DIPLOID PASPALUM SPECIES

1978 ◽  
Vol 20 (3) ◽  
pp. 365-372 ◽  
Author(s):  
Byron L. Burson
Keyword(s):  
Chromosome Number ◽  
Chromosome Pairing ◽  
Mean Frequency ◽  
Hybrid Plants ◽  
The Mean ◽  
The Cross ◽  
Relationship Of ◽  
The Relationship

Paspalum conspersum Schrad. ex Schult., 2n = 4x = 40, was crossed with P. intermedium Munro ex Morong, 2n = 2x = 20, and P. jurgensii Hackel, 2n = 2x = 20, and the hybrids were studied cytologically to determine the relationship between these species. Thirteen P. intermedium × P. conspersum hybrid plants were produced; however, only eight survived. They had a chromosome number of 2n = 3x = 30. Meiosis was irregular with a chromosome pairing relationship of 19.87 univalents, 5.03 bivalents, and 0.03 trivalents per cell. These findings suggested that the two species have a partially homologous genome. The two hybrids obtained from the cross between P. jurgensii and P. conspersum had a chromosome number of 2n = 3x = 30. The mean chromosome pairing in these hybrids was 10.12 univalents. 9.86 bivalents, 0.08 trivalents, and 0.004 quadrivalents. The close bivalent pairing and a mean frequency of 9.86 bivalents suggested that the P. jurgensii genome was homologous to one genome of P. conspersum. Limited autosyndetic pairing of the P. conspersum chromosomes was also detected in both groups of hybrids. A standardization of genome formulas for the genus was proposed in which P. intermedium, P. jurgensii, and P. conspersum were represented by genome formulas of II, JJ, and I2I2 JJ, respectively. The genome relationships and formulas were discussed for other related Paspalum species.

scholarly journals Whole-chromosome paints in maize reveal rearrangements, nuclear domains, and chromosomal relationships

2019 ◽  
Vol 116 (5) ◽  
pp. 1679-1685 ◽  
Author(s):  
Patrice S. Albert ◽  
Tao Zhang ◽  
Kassandra Semrau ◽  
Jean-Marie Rouillard ◽  
Yu-Hsin Kao ◽  
...  
Keyword(s):  
B Chromosome ◽  
Root Tip ◽  
Interphase Nuclei ◽  
Homologous Chromosomes ◽  
Complete Set ◽  
Nuclear Domains ◽  
Relationship Of ◽  
The Relationship ◽  
Painting Probes ◽  
Evolution Of Genomes

Whole-chromosome painting probes were developed for each of the 10 chromosomes of maize by producing amplifiable libraries of unique sequences of oligonucleotides that can generate labeled probes through transcription reactions. These paints allow identification of individual homologous chromosomes for many applications as demonstrated in somatic root tip metaphase cells, in the pachytene stage of meiosis, and in interphase nuclei. Several chromosomal aberrations were examined as proof of concept for study of various rearrangements using probes that cover the entire chromosome and that label diverse varieties. The relationship of the supernumerary B chromosome and the normal chromosomes was examined with the finding that there is no detectable homology between any of the normal A chromosomes and the B chromosome. Combined with other chromosome-labeling techniques, a complete set of whole-chromosome oligonucleotide paints lays the foundation for future studies of the structure, organization, and evolution of genomes.

Factors directing telomere dynamics in synaptic meiosis

2006 ◽  
Vol 34 (4) ◽  
pp. 550-553 ◽  
Author(s):  
H. Scherthan
Keyword(s):  
Nuclear Envelope ◽  
Budding Yeast ◽  
S Phase ◽  
Homologous Chromosomes ◽  
Prophase I ◽  
Yeast Meiosis ◽  
Bouquet Stage ◽  
Different Levels ◽  
Telomere Dynamics ◽  
Meiosis I

Meiosis creates haploid cells from diploid progenitors. Homologous chromosomes are moved, paired and segregated from each other in a specialized meiosis I division. A second division that lacks a preceding S-phase produces haploid cells. In prophase I, chromosomes attach with their telomeres to the nuclear envelope and undergo oscillating movements that become restricted to a limited nuclear sector during the widely conserved bouquet stage. Recent observations in budding yeast meiosis suggest that telomere clustering depends on actin, whereas exit from the bouquet stage requires meiotic cohesin. Telomere clustering may also be modulated by progression in recombination. These observations suggest that the unique meiotic nuclear topology and telomere dynamics are regulated at different levels.

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