|
Condensins
Condensins are large protein complexes that play a central role in chromosome condensation and segregation during mitosis and meiosis (Figure 1). Their subunits were originally identified as major components of mitotic chromosomes assembled in ''Xenopus'' egg extracts. Subunit composition and phylogeny Eukaryotic types Many eukaryotic cells possess two different types of condensin complexes, known as condensin I and condensin II, each of which is composed of five subunits (Figure 2). Condensins I and II share the same pair of core subunits, SMC2 and SMC4, both belonging to a large family of chromosomal ATPases, known as SMC proteins (SMC stands for Structural Maintenance of Chromosomes). Each of the complexes contains a distinct set of non-SMC regulatory subunits (a kleisin subunit and a pair of HEAT repeat subunits). Both complexes are large, having a total molecular mass of 650-700 kDa. The core subunits condensins (SMC2 and SMC4) are conserved among all eukaryotic speci ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chromosome Condensation
Chromosome condensation refers to the process by which dispersed interphase chromatin is transformed into a set of compact, rod-shaped structures during mitosis and meiosis (Figure 1). The term "chromosome condensation" has long been used in biology. However, it is now increasingly recognized that mitotic chromosome condensation proceeds through mechanisms distinct from those governing "condensation" in physical chemistry (e.g., gas-to-liquid phase transitions) or the formation of "biomolecular condensates" in cell biology. Consequently, some researchers have argued that the term "chromosome condensation" may be misleading in this context. For this reason, alternative terms such as "chromosome assembly" or "chromosome formation" are also commonly used. Processes of chromosome condensation From DNA to chromosomes A diploid human cell contains 46 chromosomes: 22 pairs of autosomes (22 × 2) and one pair of sex chromosomes (XX or XY). The total length of DNA within a single nucleus re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
SMC Protein
SMC proteins represent a large family of ATPases that participate in many aspects of higher-order chromosome organization and dynamics. SMC proteins are widely conserved across bacteria, archaea, and eukaryotes. In eukaryotes, they function as the core ATPase subunits of large protein complexes such as condensin, cohesin, and SMC5/6. The term SMC derives from a mutant strain of ''Saccharomyces cerevisiae'' named ''smc1'' (stability of mini-chromosomes 1), which was identified based on its defect in maintaining the stability of mini-chromosomes. After the gene product of ''SMC1'' was characterized, and homologous proteins were found to be essential for chromosome structure and dynamics in many organisms, the acronym SMC was redefined to stand for "Structural Maintenance of Chromosomes". Classification Eukaryotic SMCs Eukaryotes have at least six SMC proteins in individual organisms, and they form three distinct heterodimers with specialized functions: *SMC1-SMC3: A pair of SM ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HEAT Repeat
A HEAT repeat is a Protein tandem repeats, protein tandem repeat structural motif composed of two alpha helices linked by a short loop. HEAT repeats can form alpha solenoids, a type of solenoid protein domain found in a number of cytoplasmic proteins. The name "HEAT" is an acronym for four proteins in which this repeat structure is found: huntingtin, Huntingtin, elongation factor 3 (EF3), protein phosphatase 2A (PP2A), and the yeast kinase TOR1. HEAT repeats form extended superhelical structures which are often involved in intracellular transport; they are structurally related to armadillo repeats. The nuclear transport protein KPNB1, importin beta contains 19 HEAT repeats. Various HEAT repeat proteins and their structures Representative examples of HEAT repeat proteins include importin β (also known as karyopherin β) family, regulatory subunits of condensin and cohesin, separase, PIKKs (phosphatidylinositol 3-kinase-related protein kinases) such as ATM (w:Ataxia telangiectasia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schizosaccharomyces Pombe
''Schizosaccharomyces pombe'', also called "fission yeast", is a species of yeast used in traditional brewing and as a model organism in molecular and cell biology. It is a unicellular eukaryote, whose cells are rod-shaped. Cells typically measure 3 to 4 micrometres in diameter and 7 to 14 micrometres in length. Its genome, which is approximately 14.1 million base pairs, is estimated to contain 4,970 protein-coding genes and at least 450 non-coding RNAs. These cells maintain their shape by growing exclusively through the cell tips and divide by medial fission to produce two daughter cells of equal size, which makes them a powerful tool in cell cycle research. Fission yeast was isolated in 1893 by Paul Lindner from East African millet beer. The species name ''pombe'' is the Swahili word for beer. It was first developed as an experimental model in the 1950s: by Urs Leupold for studying genetics, and by Murdoch Mitchison for studying the cell cycle. Paul Nurse, a fission ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyanidioschyzon Merolae
''Cyanidioschyzon merolae'' is a small (2μm), club-shaped, unicellular haploid red alga adapted to high sulfur acidic hot spring environments (pH 1.5, 45 °C). The cellular architecture of ''C. merolae'' is extremely simple, containing only a single chloroplast and a single mitochondrion and lacking a vacuole and cell wall. In addition, the cellular and organelle divisions can be synchronized. For these reasons, ''C. merolae'' is considered an excellent model system for study of cellular and organelle division processes, as well as biochemistry and structural biology. The organism's genome was the first full algal genome to be sequenced in 2004; its plastid was sequenced in 2000 and 2003, and its mitochondrion in 1998. The organism has been considered the simplest of eukaryotic cells for its minimalist cellular organization. Isolation and growth in culture Originally isolated by De Luca in 1978 from the solfatane fumaroles of Campi Flegrei ( Naples, Italy), ''C. merola ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Arabidopsis Thaliana
''Arabidopsis thaliana'', the thale cress, mouse-ear cress or arabidopsis, is a small plant from the mustard family (Brassicaceae), native to Eurasia and Africa. Commonly found along the shoulders of roads and in disturbed land, it is generally considered a weed. A winter annual with a relatively short lifecycle, ''A. thaliana'' is a popular model organism in plant biology and genetics. For a complex multicellular eukaryote, ''A. thaliana'' has a relatively small genome of around 135 Base pair#Length measurements, megabase pairs. It was the first plant to have its genome sequenced, and is an important tool for understanding the molecular biology of many plant traits, including flower development and phototropism, light sensing. Description ''Arabidopsis thaliana'' is an annual plant, annual (rarely biennial plant, biennial) plant, usually growing to 20–25 cm tall. The leaf, leaves form a rosette at the base of the plant, with a few leaves also on the flowering Plant ste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paralog
Sequence homology is the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry because of three phenomena: either a speciation event (orthologs), or a duplication event (paralogs), or else a horizontal (or lateral) gene transfer event (xenologs). Homology among DNA, RNA, or proteins is typically inferred from their nucleotide or amino acid sequence similarity. Significant similarity is strong evidence that two sequences are related by evolutionary changes from a common ancestral sequence. Alignments of multiple sequences are used to indicate which regions of each sequence are homologous. Identity, similarity, and conservation The term "percent homology" is often used to mean "sequence similarity”, that is the percentage of identical residues (''percent identity''), or the percentage of residues conserved with similar physicochemical properties ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ciliate
The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to flagellum, eukaryotic flagella, but are in general shorter and present in much larger numbers, with a different wikt:undulating, undulating pattern than flagella. Cilia occur in all members of the group (although the peculiar Suctoria only have them for part of their biological life cycle, life cycle) and are variously used in swimming, crawling, attachment, feeding, and sensation. Ciliates are an important group of protists, common almost anywhere there is water—in lakes, ponds, oceans, rivers, and soils, including anoxic and oxygen-depleted habitats. About 4,500 unique free-living species have been described, and the potential number of extant species is estimated at 27,000–40,000. Included in this number are many Ectosymbiosis, ectosymbiotic and endosymbiotic species, as well as some Obligate parasite, obligate and Facultative paras ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrahymena Thermophila
''Tetrahymena thermophila'' is a species of Ciliophora in the family Tetrahymenidae. It is a free living protozoon and occurs in fresh water. There is little information on the ecology and natural history of this species, but it is the most widely known and widely studied species in the genus '' Tetrahymena''. The species has been used as a model organism for molecular and cellular biology. It has also helped in the discovery of new genes as well as helping to understand the mechanisms of function of certain genes. Studies on this species have contributed to major discoveries in biology. For example, the MAT locus found in this species has provided a foundation for the evolution of mating systems. The species was at first considered to be a form of '' Tetrahymena pyriformis''. '' T. malaccensis'' is the closest relative to''T. thermophila''. Characteristics It is about 50 μm long. One famous trait this species is known for is that has 7 different mating types, unlike ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fungus
A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one of the kingdom (biology)#Six kingdoms (1998), traditional eukaryotic kingdoms, along with Animalia, Plantae, and either Protista or Protozoa and Chromista. A characteristic that places fungi in a different kingdom from plants, bacteria, and some protists is chitin in their cell walls. Fungi, like animals, are heterotrophs; they acquire their food by absorbing dissolved molecules, typically by secreting digestive enzymes into their environment. Fungi do not photosynthesize. Growth is their means of motility, mobility, except for spores (a few of which are flagellated), which may travel through the air or water. Fungi are the principal decomposers in ecological systems. These and other differences place fungi in a single group of related o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paralogs
Sequence homology is the biological homology between DNA, RNA, or protein sequences, defined in terms of shared ancestry in the evolutionary history of life. Two segments of DNA can have shared ancestry because of three phenomena: either a speciation event (orthologs), or a duplication event (paralogs), or else a horizontal (or lateral) gene transfer event (xenologs). Homology among DNA, RNA, or proteins is typically inferred from their nucleotide or amino acid sequence similarity. Significant similarity is strong evidence that two sequences are related by evolutionary changes from a common ancestral sequence. Alignments of multiple sequences are used to indicate which regions of each sequence are homologous. Identity, similarity, and conservation The term "percent homology" is often used to mean "sequence similarity”, that is the percentage of identical residues (''percent identity''), or the percentage of residues conserved with similar physicochemical properties (''p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
