1.
Mitosis
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In cell biology, mitosis is a part of the cell cycle when replicated chromosomes are separated into two new nuclei. Mitosis and cytokinesis together define the phase of an animal cell cycle—the division of the mother cell into two daughter cells genetically identical to each other. The process of mitosis is divided into stages corresponding to the completion of one set of activities and these stages are prophase, prometaphase, metaphase, anaphase, and telophase. During mitosis, the chromosomes, which have already duplicated, condense, the result is two genetically identical daughter nuclei. The rest of the cell may then continue to divide by cytokinesis to produce two daughter cells, producing three or more daughter cells instead of normal two is a mitotic error called tripolar mitosis or multipolar mitosis. Other errors during mitosis can induce apoptosis or cause mutations, certain types of cancer can arise from such mutations. Mitosis occurs only in eukaryotic cells, prokaryotic cells, which lack a nucleus, divide by a different process called binary fission. Most animal cells undergo a change, known as mitotic cell rounding. Most human cells are produced by cell division. Important exceptions include the gametes – sperm and egg cells – which are produced by meiosis, german zoologist Otto Bütschli might have claimed the discovery of the process presently known as mitosis, a term coined by Walther Flemming in 1882. Mitosis was discovered in frog, rabbit, and cat cornea cells in 1873, the term is derived from the Greek word μίτος mitos warp thread. The primary result of mitosis and cytokinesis is the transfer of a parent cells genome into two daughter cells, the genome is composed of a number of chromosomes—complexes of tightly coiled DNA that contain genetic information vital for proper cell function. Because each resultant daughter cell should be identical to the parent cell. This occurs during the S phase of interphase, chromosome duplication results in two identical sister chromatids bound together by cohesin proteins at the centromere. When mitosis begins, the chromosomes condense and become visible, in some eukaryotes, for example animals, the nuclear envelope, which segregates the DNA from the cytoplasm, disintegrates into small vesicles. The nucleolus, which makes ribosomes in the cell, also disappears, microtubules project from opposite ends of the cell, attach to the centromeres, and align the chromosomes centrally within the cell. The microtubules then contract to pull the chromatids of each chromosome apart. Sister chromatids at this point are called daughter chromosomes, as the cell elongates, corresponding daughter chromosomes are pulled toward opposite ends of the cell and condense maximally in late anaphase
2.
Chromosome
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A chromosome is a DNA molecule with part or all of the genetic material of an organism. Prokaryotes usually have one single circular chromosome, whereas most eukaryotes are diploid, chromosomes in eukaryotes are composed of chromatin fiber. Chromatin fiber is made of nucleosomes, a nucleosome is a histone octamer with part of a longer DNA strand attached to and wrapped around it. Chromatin fiber, together with associated proteins is known as chromatin, chromatin is present in most cells, with a few exceptions, for example, red blood cells. Occurring only in the nucleus of cells, chromatin contains the vast majority of DNA, except for a small amount inherited maternally. Chromosomes are normally visible under a microscope only when the cell is undergoing the metaphase of cell division. Before this happens every chromosome is copied once, and the copy is joined to the original by a centromere resulting in an X-shaped structure, the original chromosome and the copy are now called sister chromatids. During metaphase, when a chromosome is in its most condensed state, in this highly condensed form chromosomes are easiest to distinguish and study. In prokaryotic cells, chromatin occurs free-floating in cytoplasm, as these cells lack organelles, the main information-carrying macromolecule is a single piece of coiled double-helix DNA, containing many genes, regulatory elements and other noncoding DNA. The DNA-bound macromolecules are proteins that serve to package the DNA, chromosomes vary widely between different organisms. Some species such as certain bacteria also contain plasmids or other extrachromosomal DNA and these are circular structures in the cytoplasm that contain cellular DNA and play a role in horizontal gene transfer. Chromosomal recombination during meiosis and subsequent sexual reproduction plays a significant role in genetic diversity. In prokaryotes and viruses, the DNA is often densely packed and organized, in the case of archaea, by homologs to eukaryotic histones, small circular genomes called plasmids are often found in bacteria and also in mitochondria and chloroplasts, reflecting their bacterial origins. Some use the term chromosome in a sense, to refer to the individualized portions of chromatin in cells. However, others use the concept in a sense, to refer to the individualized portions of chromatin during cell division. The word chromosome comes from the Greek χρῶμα and σῶμα, describing their strong staining by particular dyes, schleiden, Virchow and Bütschli were among the first scientists who recognized the structures now so familiar to everyone as chromosomes. The term was coined by von Waldeyer-Hartz, referring to the term chromatin, in a series of experiments beginning in the mid-1880s, Theodor Boveri gave the definitive demonstration that chromosomes are the vectors of heredity. His two principles were the continuity of chromosomes and the individuality of chromosomes and it is the second of these principles that was so original
3.
Protein
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Proteins are large biomolecules, or macromolecules, consisting of one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, a linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide, short polypeptides, containing less than 20–30 residues, are rarely considered to be proteins and are commonly called peptides, or sometimes oligopeptides. The individual amino acid residues are bonded together by peptide bonds, the sequence of amino acid residues in a protein is defined by the sequence of a gene, which is encoded in the genetic code. In general, the code specifies 20 standard amino acids, however. Sometimes proteins have non-peptide groups attached, which can be called prosthetic groups or cofactors, proteins can also work together to achieve a particular function, and they often associate to form stable protein complexes. Once formed, proteins only exist for a period of time and are then degraded and recycled by the cells machinery through the process of protein turnover. A proteins lifespan is measured in terms of its half-life and covers a wide range and they can exist for minutes or years with an average lifespan of 1–2 days in mammalian cells. Abnormal and or misfolded proteins are degraded more rapidly due to being targeted for destruction or due to being unstable. Like other biological macromolecules such as polysaccharides and nucleic acids, proteins are essential parts of organisms, many proteins are enzymes that catalyse biochemical reactions and are vital to metabolism. Proteins also have structural or mechanical functions, such as actin and myosin in muscle and the proteins in the cytoskeleton, other proteins are important in cell signaling, immune responses, cell adhesion, and the cell cycle. In animals, proteins are needed in the diet to provide the essential amino acids that cannot be synthesized, digestion breaks the proteins down for use in the metabolism. Methods commonly used to study structure and function include immunohistochemistry, site-directed mutagenesis, X-ray crystallography, nuclear magnetic resonance. Most proteins consist of linear polymers built from series of up to 20 different L-α-amino acids, all proteinogenic amino acids possess common structural features, including an α-carbon to which an amino group, a carboxyl group, and a variable side chain are bonded. Only proline differs from this structure as it contains an unusual ring to the N-end amine group. The amino acids in a chain are linked by peptide bonds. Once linked in the chain, an individual amino acid is called a residue, and the linked series of carbon, nitrogen. The peptide bond has two forms that contribute some double-bond character and inhibit rotation around its axis, so that the alpha carbons are roughly coplanar
4.
Cyclin
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Cyclins are a family of proteins that control the progression of cells through the cell cycle by activating cyclin-dependent kinase enzymes. Cyclins were originally discovered by R. Timothy Hunt in 1982 while studying the cell cycle of sea urchins, in an interview for The Life Scientific hosted by Jim Al-Khalili, R. Timothy Hunt explained that the name cyclin was originally named after his hobby cycling. It was only after the naming did its importance in the cell cycle become apparent, as it was appropriate the name stuck. R. Timothy Hunt, By the way, the cyclin, which I coined, was really a joke, its because I liked cycling so much at the time. Cyclins were originally named because their concentration varies in a fashion during the cell cycle. A cyclin forms a complex with Cdk, which begins to activate the Cdk, complex formation results in activation of the Cdk active site. Cyclins themselves have no enzymatic activity but have binding sites for some substrates, Cyclins, when bound with the dependent kinases, such as the p34/cdc2/cdk1 protein, form the maturation-promoting factor. MPFs activate other proteins through phosphorylation and these phosphorylated proteins, in turn, are responsible for specific events during cycle division such as microtubule formation and chromatin remodeling. Cyclins can be divided into four classes based on their behavior in the cycle of vertebrate somatic cells and yeast cells, G1 cyclins, G1/S cyclins, S cyclins. This division is useful when talking about most cell cycles, G1/S Cyclins rise in late G1 and fall in early S phase. The Cdk- G1/S cyclin complex begins to induce the initial processes of DNA replication, the cyclins also promote other activities to progress the cell cycle, such as centrosome duplication in vertebrates or spindle pole body in yeast. The rise in presence of G1/S cyclins is paralleled by a rise in S cyclins, G1 cyclins do not behave like the other cyclins, in that the concentrations increase gradually, throughout the cell cycle based on cell growth and the external growth-regulatory signals. The presence of G cyclins coordinate cell growth with the entry to a new cell cycle, S cyclins bind to Cdk and the complex directly induces DNA replication. The levels of S cyclins remain high, not only throughout S phase, M cyclin concentrations rise as the cell begins to enter mitosis and the concentrations peak at metaphase. Cell changes in the cell cycle like the assembly of mitotic spindles, the destruction of M cyclins during metaphase and anaphase, after the Spindle Assembly Checkpoint is satisfied, causes the exit of mitosis and cytokinesis. Cyclins are generally different from each other in primary structure. However, all members of the family are similar in 100 amino acids that make up the cyclin box. Cyclins contain two domains of a similar fold, the first located at the N-terminus and the second at the C-terminus
5.
Securin
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Securin is a protein involved in control of the metaphase-anaphase transition and anaphase onset. Securin is initially present in the cytoplasm and binds to separase, separase is vital for onset of anaphase. This securin-separase complex is maintained when securin is phosphorylated by Cdk1, when bound to securin, separase is not functional. In addition, both securin and separase are well-conserved proteins, note that separase cannot function without initially forming the securin-separase complex. This is because securin helps properly fold separase into the functional conformation, however, yeast does not appear to require securin to form functional separase as anaphase occurs in yeast with a securin deletion mutation. Securin has 5 known phosphorylation sites that are targets of Cdk1,2 sites at the N-terminal in the Ken-Box and D-box region are known to affect APC recognition and ubiquitination, to initiate the onset of anaphase, securin is dephosphorylated by Cdc14 and other phosphatases. Dephosphorylated securin is recognized by the Anaphase-Promoting Complex bound primarily to Cdc20, the APCCdc20 complex ubiquitinates securin and targets it for degradation. This results in free separase that is able to destroy cohesin and it is thought that securin integrates multiple regulatory inputs to make separase activation switch-like, resulting in sudden, coordinated anaphase. This likely involves a network with several loops, including positive feedback which leads to switch-like behavior. One proposed signaling pathway generating switch-like behavior contains a positive feedback loop for activation of Cdc14 by separase, in addition, these mutant strains exhibited very high rates of mis-segregation compared to normal behavior. Switch-like characteristics are necessary to trigger quick, coordinated chromosomal segregation in anaphase and this means that strong inactivation of separase by securin followed by sudden, rapid destruction of securin and activation of separase is vital for proper anaphase. Overall, securin and separase act in an anaphase-regulating network, figure 4 depicts a potential network diagram
6.
Kinetochore
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Kinetochore, protein structure found at the centromere of a chromatid to which microtubules attach to during cell division. The kinetochore is a structure on chromatids where the spindle fibers attach during cell division to pull sister chromatids apart. Their proteins help to hold the sister chromatids together and also play a role in chromosome editing, the kinetochore forms in eukaryotes, assembles on the centromere and links the chromosome to microtubule polymers from the mitotic spindle during mitosis and meiosis. Monocentric organisms, including vertebrates, fungi, and most plants, have a single region on each chromosome which assembles one kinetochore. Holocentric organisms, such as nematodes and some plants, assemble a kinetochore along the length of a chromosome. Kinetochores start, control, and supervise the movements of chromosomes during cell division. Thus, the kinetochore is essential for the segregation that is classically associated with mitosis and meiosis. Even the simplest kinetochores consist of more than 19 different proteins, many of these proteins are conserved between eukaryotic species, including a specialized histone H3 variant which helps the kinetochore associate with DNA. Other proteins in the kinetochore attach it to the microtubules of the mitotic spindle, there are also motor proteins, including both dynein and kinesin, which generate forces that move chromosomes during mitosis. On the other hand, MTs are metastable polymers made of α- and β-tubulin, MTs are highly dynamic structures, whose behavior is integrated with kinetochore function to control chromosome movement and segregation. The kinetochore is composed of layers, observed initially by conventional fixation and staining methods of electron microscopy. The deepest layer in the kinetochore is the plate, which is organized on a chromatin structure containing nucleosomes presenting a specialized histone, auxiliary proteins. DNA organization in the centromere is one of the least known aspects in vertebrate kinetochores, the inner plate appears like a discrete heterochromatin domain throughout the cell cycle. Outside the inner plate we find the outer plate, composed mostly by proteins and this structure is assembled in the surface of the chromosomes when the nuclear envelope breaks down. The outer plate in vertebrate kinetochores contains about 20 anchoring sites for MTs ends, the outermost domain in the kinetochore forms a fibrous corona, which can be visualized by conventional microscopy, yet only in absence of MTs. This corona is formed by a network of resident and temporary proteins implicated in the spindle checkpoint, in MTs anchoring. During mitosis, each sister chromatid forming the complete chromosome has its own kinetochore, distinct sister kinetochores can be observed at first at the end of G2 phase in cultured mammalian cells. These early kinetochores show a mature laminar structure before the nuclear envelope breaks down, yet no simple linear route can describe the data obtained so far
7.
Proteasome
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Proteasomes are protein complexes inside all eukaryotes and archaea, and in some bacteria. In eukaryotes, proteasomes are located in the nucleus and the cytoplasm, the main function of the proteasome is to degrade unneeded or damaged proteins by proteolysis, a chemical reaction that breaks peptide bonds. Enzymes that help such reactions are called proteases, proteasomes are part of a major mechanism by which cells regulate the concentration of particular proteins and degrade misfolded proteins. The degradation process yields peptides of about seven to eight amino acids long, proteins are tagged for degradation with a small protein called ubiquitin. The tagging reaction is catalyzed by enzymes called ubiquitin ligases, once a protein is tagged with a single ubiquitin molecule, this is a signal to other ligases to attach additional ubiquitin molecules. The result is a chain that is bound by the proteasome. In structure, the proteasome is a complex containing a core of four stacked rings forming a central pore. Each ring is composed of seven individual proteins, the inner two rings are made of seven β subunits that contain three to seven protease active sites. These sites are located on the surface of the rings. The outer two rings each contain seven α subunits whose function is to maintain a gate through which proteins enter the barrel and these α subunits are controlled by binding to cap structures or regulatory particles that recognize polyubiquitin tags attached to protein substrates and initiate the degradation process. The overall system of ubiquitination and proteasomal degradation is known as the ubiquitin-proteasome system, the proteasomal degradation pathway is essential for many cellular processes, including the cell cycle, the regulation of gene expression, and responses to oxidative stress. However, work by Alfred Goldberg in 1977 on ATP-dependent protein degradation in reticulocytes and this was shown in 1978 to be composed of several distinct protein chains, a novelty among proteases at the time. It was then discovered that an identified protein associated with proteolytic degradation. The proteolytic activities of this system was isolated as a complex originally called the multi-catalytic proteinase complex by Sherwin Wilk. Later, the ATP-dependent proteolytic complex that was responsible for ubiquitin-dependent protein degradation was discovered and was called the 26S proteasome, hershkos year-long sabbatical in the laboratory of Irwin Rose at the Fox Chase Cancer Center provided key conceptual insights, though Rose later downplayed his role in the discovery. The three shared the 2004 Nobel Prize in Chemistry for their work in discovering this system, the proteasome subcomponents are often referred to by their Svedberg sedimentation coefficient. The core is hollow and provides a cavity in which proteins are degraded. The inner two rings each consist of seven β subunits and contain the active sites that perform the proteolysis reactions
8.
Ancient Greek
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Ancient Greek includes the forms of Greek used in ancient Greece and the ancient world from around the 9th century BC to the 6th century AD. It is often divided into the Archaic period, Classical period. It is antedated in the second millennium BC by Mycenaean Greek, the language of the Hellenistic phase is known as Koine. Koine is regarded as a historical stage of its own, although in its earliest form it closely resembled Attic Greek. Prior to the Koine period, Greek of the classic and earlier periods included several regional dialects, Ancient Greek was the language of Homer and of fifth-century Athenian historians, playwrights, and philosophers. It has contributed many words to English vocabulary and has been a subject of study in educational institutions of the Western world since the Renaissance. This article primarily contains information about the Epic and Classical phases of the language, Ancient Greek was a pluricentric language, divided into many dialects. The main dialect groups are Attic and Ionic, Aeolic, Arcadocypriot, some dialects are found in standardized literary forms used in literature, while others are attested only in inscriptions. There are also several historical forms, homeric Greek is a literary form of Archaic Greek used in the epic poems, the Iliad and Odyssey, and in later poems by other authors. Homeric Greek had significant differences in grammar and pronunciation from Classical Attic, the origins, early form and development of the Hellenic language family are not well understood because of a lack of contemporaneous evidence. Several theories exist about what Hellenic dialect groups may have existed between the divergence of early Greek-like speech from the common Proto-Indo-European language and the Classical period and they have the same general outline, but differ in some of the detail. The invasion would not be Dorian unless the invaders had some relationship to the historical Dorians. The invasion is known to have displaced population to the later Attic-Ionic regions, the Greeks of this period believed there were three major divisions of all Greek people—Dorians, Aeolians, and Ionians, each with their own defining and distinctive dialects. Often non-west is called East Greek, Arcadocypriot apparently descended more closely from the Mycenaean Greek of the Bronze Age. Boeotian had come under a strong Northwest Greek influence, and can in some respects be considered a transitional dialect, thessalian likewise had come under Northwest Greek influence, though to a lesser degree. Most of the dialect sub-groups listed above had further subdivisions, generally equivalent to a city-state and its surrounding territory, Doric notably had several intermediate divisions as well, into Island Doric, Southern Peloponnesus Doric, and Northern Peloponnesus Doric. The Lesbian dialect was Aeolic Greek and this dialect slowly replaced most of the older dialects, although Doric dialect has survived in the Tsakonian language, which is spoken in the region of modern Sparta. Doric has also passed down its aorist terminations into most verbs of Demotic Greek, by about the 6th century AD, the Koine had slowly metamorphosized into Medieval Greek
9.
Prophase
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Prophase, is a stage of Mitosis. This is when the chromatin condenses into two rod-shaped structures called chromosomes in which the chromatin becomes visible and this process, known as chromatin condensation, is involved with the condensin complex. Since the genetic material has been replicated in the interphase of the cell cycle. Those copies are called sister chromatids and they are attached to each other at a DNA element present on every chromosome called the centromere, also during prophase, giemsa staining can be applied to elicit G-banding in chromosomes. An important organelle in mitosis is the centrosome, the organizing center in metazoans. During prophase, the two centrosomes, which replicate independently of mitosis, have their microtubule-activity increased due to the recruitment of γ-tubulin, the centrosomes will be pushed apart to opposite ends of the cell nucleus by the action of molecular motors acting on the microtubules. At the end of prophase, the tiny nucleolus within the nucleus dissolves, the nucleolus starts moving towards the nuclear membrane at the beginning of prophase, and its disintegration occurs near the nuclear envelope. Its contents are dispersed in masses, basically, the chromatin in the nucleus coils into chromosomes. The centrosomes move to opposite poles of the cell, forming a bridge of spindle fibers, at the end of prophase, the nucleolus disperses. In prometaphase, the step of mitosis, the nuclear membrane breaks apart. Interphase Metaphase Anaphase Telophase Farhan Phase Media related to Prophase at Wikimedia Commons
10.
Cyclin-dependent kinase 1
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It has been highly studied in the budding yeast S. cerevisiae, and the fission yeast S. pombe, where it is encoded by genes cdc28 and cdc2, respectively. In humans, Cdk1 is encoded by the CDC2 gene, with its cyclin partners, Cdk1 forms complexes that phosphorylate a variety of target substrates, phosphorylation of these proteins leads to cell cycle progression. Cdk1 is a protein, and is highly conserved. The human homolog of Cdk1, CDC2, shares approximately 63% amino-acid identity with its yeast homolog, furthermore, human CDC2 is capable of rescuing fission yeast carrying a cdc2 mutation. Cdk1 is comprised mostly by the protein kinase motif, which other protein kinases share. Cdk1, like other kinases, contains a cleft in which ATP fits, substrates of Cdk1 bind near the mouth of the cleft, and Cdk1 residues catalyze the covalent bonding of the γ-phosphate to the oxygen of the hydroxyl serine/threonine of the substrate. In addition to this core, Cdk1, like other cyclin-dependent kinases, contains a T-loop. Cdk1 also contains a PSTAIRE helix, which, upon binding, moves and rearranges the active site. When bound to its partners, Cdk1 phosphorylation leads to cell cycle progression. Cdk1 activity is best understood in S. cerevisiae, so Cdk1 S. cerevisiae activity is described here, in the budding yeast, initial cell cycle entry is controlled by two regulatory complexes, SBF and MBF. These two complexes control G1/S gene transcription, however, they are normally inactive, G1/S cyclin-Cdk1 activity leads to preparation for S phase entry, and a rise in the S cyclins. Clb5, 6-Cdk1 complexes directly lead to replication origin initiation, however, they are inhibited by Sic1, cln1,2 and/or Clb5, 6-Cdk1 complex activity leads to a sudden drop in Sic1 levels, allowing for coherent S phase entry. Finally, phosphorylation by M cyclins in complex with Cdk1 leads to spindle assembly, Cdk1 phosphorylation also leads to the activation of the ubiquitin-protein ligase APCCdc20, an activation which allows for chromatid segregation and, furthermore, degradation of M-phase cyclins. This destruction of M cyclins leads to the events of mitosis. Given its essential role in cell cycle progression, Cdk1 is highly regulated, most obviously, Cdk1 is regulated by its binding with its cyclin partners. Cyclin binding alters access to the site of Cdk1, allowing for Cdk1 activity, furthermore. At least some cyclins contain a hydrophobic patch which may interact with substrates. Furthermore, cyclins can target Cdk1 to particular subcellular locations, in addition to regulation by cyclins, Cdk1 is regulated by phosphorylation
11.
Cell cycle
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The cell cycle or cell-division cycle is the series of events that take place in a cell leading to its division and duplication of its DNA to produce two daughter cells. In bacteria, which lack a nucleus, the cell cycle is divided into the B, C. The B period extends from the end of cell division to the beginning of DNA replication, DNA replication occurs during the C period. The D period refers to the stage between the end of DNA replication and the splitting of the cell into two daughter cells. In cells with a nucleus, as in eukaryotes, the cycle is also divided into three periods, interphase, the mitotic phase, and cytokinesis. During interphase, the cell grows, accumulating nutrients needed for mitosis, preparing it for cell division, during the mitotic phase, the chromosomes separate. During the final stage, cytokinesis, the chromosomes and cytoplasm separate into two new daughter cells, to ensure the proper division of the cell, there are control mechanisms known as cell cycle checkpoints. After cell division, each of the cells begin the interphase of a new cycle. The cell cycle consists of four phases, G1 phase, S phase, G2 phase. Activation of each phase is dependent on the progression and completion of the previous one. Cells that have temporarily or reversibly stopped dividing are said to have entered a state of quiescence called G0 phase, after cell division, each of the daughter cells begin the interphase of a new cycle. G0 is a phase where the cell has left the cycle and has stopped dividing. The cell cycle starts with this phase, the word post-mitotic is sometimes used to refer to both quiescent and senescent cells. Non proliferative cells in multicellular eukaryotes generally enter the quiescent G0 state from G1 and may remain quiescent for long periods of time and this is very common for cells that are fully differentiated. Cellular senescence occurs in response to DNA damage and external stress, some cells enter the G0 phase semi-permanently, and are considered post-mitotic e. g. some liver, kidney, stomach cells. Many cells do not enter G0 and continue to divide throughout an organisms life, before a cell can enter cell division, it needs to take in nutrients. All of the preparations are done during interphase, interphase is a series of changes that takes place in a newly formed cell and its nucleus, before it becomes capable of division again. It is also called preparatory phase or intermitosis, previously it was called resting stage because there is no apparent activity related to cell division. Typically interphase lasts for at least 90% of the total time required for the cell cycle
12.
Metaphase
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Metaphase is a stage of mitosis in the eukaryotic cell cycle in which chromosomes are at their second-most condensed and coiled stage. These chromosomes, carrying information, align in the equator of the cell before being separated into each of the two daughter cells. Metaphase accounts for approximately 4% of the cell cycles duration, preceded by events in prometaphase and followed by anaphase, microtubules formed in prophase have already found and attached themselves to kinetochores in metaphase. In metaphase, the centromeres of the chromosomes convene themselves on the metaphase plate, in certain types of cells, chromosomes do not line up at the metaphase plate and instead move back and forth between the poles randomly, only roughly lining up along the middleline. One of the cell cycle checkpoints occurs during prometaphase and metaphase, only after all chromosomes have become aligned at the metaphase plate, when every kinetochore is properly attached to a bundle of microtubules, does the cell enter anaphase. Such a signal creates the mitotic spindle checkpoint and this would be accomplished by regulation of the anaphase-promoting complex, securin, and separase. The analysis of chromosomes is one of the main tools of classical cytogenetics. Chromosomes are condensed and highly coiled in metaphase, which makes them most suitable for visual analysis, Metaphase chromosomes make the classical picture of chromosomes. For classical cytogenetic analyses, cells are grown in short term culture, further they are used for slide preparation and banding of chromosomes to be visualised under microscope to study structure and number of chromosomes. Staining of the slides, often with Giemsa or Quinacrine, produces a pattern of in total up to several hundred bands, normal metaphase spreads are used in methods like FISH and as a hybridization matrix for comparative genomic hybridization experiments. Malignant cells from solid tumors or leukemia samples can also be used for analysis to generate metaphase preparations. Interphase Prophase Anaphase Telophase Media related to Metaphase at Wikimedia Commons
Media related to Anaphase at Wikimedia Commons