Centrosomes Essay

833 Words2 Pages
bulb-icon

Recommended: 10.2 mitosis the process of cell division

Centrosomes are cytoplasmic organelles which contain two centrioles (mother and daughter centriole) positioned perpendicular to each other. Each centriole is a cylindrical structure, ~100-150 nm in diameter and 100- 400 nm in length, made up of nine microtubule triplets (singles or doublets in some cells) (Delattre and Gönczy, 2004). The centrosome is surrounded by pericentriolar material (PCM) which helps in nucleating microtubules. The PCM contains pericentrin, centrin, γ-tubulin ring complexes (γ-TuRC). The γ-TuRC initiates microtubule polymerization, which involves the repeated addition of α and β subunits. The centrosome functions as a Microtubule Organising Center (MTOC) in animal cells. Fungal and plants cells do not possess centrosomes, and instead use other MTOCs (e.g. yeast cells have Spindle Pole Bodies (SPBs)).

Centrosome biogenesis is initiated in the G1 phase. The centrosome duplication cycle which is normally coordinated with the cell cycle, also faces exceptions in the case of spermatogenesis in which centrosome duplication occurs before the second meosis, and in cancer cell. …show more content…

The two new pair of centrioles arise from the proximal end of each of the older centrioles, and elongate to reach the same length as the parent centrioles. The original mother and daughter centrioles completely separate from each other, along with their new daughter centrioles to form two new centrosomes. Each of the two resulting centrosomes thus contain one centriol from the older generation and one newly formed centriole (semiconservative replication). The PCM also gets divided between the two new centrosomes. The sequence of steps of the centrosome duplicaiton cycle shows variations in some cells. For example, in Drosophila melanogaster embryo, the PCM divides before the new daughter centrioles are

Show More
Related

  • Pros And Cons Of Meiosis

    752 Words  | 2 Pages

    Meiosis, also called reduction division, is a distinct type of cell division that is essential for sexual reproduction to occur. It is one in which two successive divisions of diploid cell occur thereby producing four genetically different haploid daughter cells, also called gametes, each with half the number of chromosomes and thus, half the total amount of genetic material as compared to the amount before meiosis began. Interphase precedes meiosis and thus, paves the way for meiosis to eventuate as the cell’s DNA replicates in the S phase yielding corresponding, identical chromosomes. Interphase sparks the marvelous process of meiosis that allows variation to transpire within the organisms it occurs, hence, giving rise to millions of organisms with unique aspects unlike any other on Earth. Because meiosis is a form of sexual reproduction itself, it is the means through which gametes are produced, each with a reduced number of chromosomes, so that when two gametes fuse during fertilization, not only do they form a diploid zygote with 46 chromosomes, but also have manifested differing features due to the rearrangement (crossing-over) of chromosomes.

    Read More

  • The Fungi Formerly Known as Dentinum Repandum

    1227 Words  | 3 Pages

    The next step includes the two nuclei of the dikaryon fusing through karyogomy (Ross 146). The resulting diploid zygotic nucleus then undergoes meiosis, and four haploid nuclei are formed in the basidium (Webster 280). The haploid nuclei move into projections on the basidium, which turn into spores. The spores are attached to the sterigmata until they are released (Ross 146). The cycle then starts over again.

    Read More

  • Epithelia Essay

    1097 Words  | 3 Pages

    Epithelia tissue : Epithelial tissue, the type of tissue that lines the surfaces and cavities of your body 's organs, epithelia may be composed of several layers of cells called compound epithelia or just a single layer known as simple epithelia.

    Read More

  • Compare and Contrast Mitosis and Meiosis

    493 Words  | 1 Pages

    In telophase, these separate chromatids uncoil to become chromosomes. This division produces two identical cells.

    Read More

  • Exploring the Dual Functions of the Pancreas

    760 Words  | 2 Pages

    The pancreas can be divided into two sections when studying the histology. The pancreas has exocrine and endocrine functions, each with unique cell types. The exocrine pancreas serves to secrete digestive enzymes into the duodenum. Some of the specific enzymes and secreted substances are Proteases, lipase, amylase, bicarbonate, and water (Bowen, “Exocrine Secretions”). These enzymes are used to break down protein, fat, and carbohydrates respectively. The bicarbonate simply act as an acid buffer to prevent damage of the small intestine as the stomach acid must be neutralized. The enzymes are created in acinar cells and the bicarbonate is synthesized in epithelial cells surrounding pancreatic ducts (Bowen “Exocrine

    Read More

  • Meiosis And Mitosis Essay

    1364 Words  | 3 Pages

    Cell division is extremely important; cells must divide in order to maintain an efficient volume to surface area ratio, allow organisms to grow and develop, and repair any damaged tissue. Cells are able to do all this through two processes: meiosis and mitosis. Without these processes, humans would not be able to do many of the basic functions we are so accustomed to, including growing, healing even the smallest cuts, and even reproducing! However, meiosis and mitosis, although both procedures for cell division, are very different.

    Read More

  • Chromosome replication

    525 Words  | 2 Pages

    Precise chromosomal DNA replication during S phase of the cell cycle is a crucial factor in the proper maintenance of the genome from generation to generation. The current “once-per-cell-cycle” model of eukaryotic chromosome duplication describes a highly coordinated process by which temporally regulated replicon clusters are sequentially activated and subsequently united to form two semi-conserved copies of the genome. Replicon clusters, or replication domains, are comprised of individual replication units that are synchronously activated at predetermined points during S phase. Bi-directional replication within each replicon is initiated at periodic AT-rich origins along each chromosome. Origins are not characterized by any specific nucleotide sequence, but rather the spatial arrangement of origin replication complexes (ORCs). Given the duration of the S phase and replication fork rate, adjacent origins must be appropriately spaced to ensure the complete replication of each replicon. Chromatin arrangement by the nuclear matrix may be the underpinning factor responsible for ORC positioning. The six subunit ORC binds to origins of replication in an ATP-dependent manner during late telophase and early G1. In yeast, each replication domain simply contains a single ORC binding site. However, more complex origins are characterized by an initiation zone where DNA synthesis may begin at numerous locations. A single round of DNA synthesis at each activated origin is achieved by “lic...

    Read More

  • Nuclear Division

    911 Words  | 2 Pages

    A chromosome is made up of two identical structures called chromatids. The process of nuclear division is called interphase; each DNA molecule in a nucleus makes an identical copy of itself. Each copy is contained in the chromatid and a characteristic narrow region called the centromere holds the two chromatids together. The centromere can be found anywhere along a chromosome but the position is the characteristic for a particular chromosome. Each Chromatid contains one DNA molecule. DNA is the molecule of inheritance and is made up of a series of genes. The fact that the two DNA molecules in the sister chromatids, and hence their genes, are identical is the key to precise nuclear division.

    Read More

  • Cytoskeleton Essay

    701 Words  | 2 Pages

    The cytoskeleton is a highly dynamic intracellular platform constituted by a three-dimensional network of proteins responsible for key cellular roles as structure and shape, cell growth and development, and offering to the cell with "motility" that being the ability of the entire cell to move and for material to be moved within the cell in a regulated fashion (vesicle trafficking)’, (intechopen 2017). The cytoskeleton is made of microtubules, filaments, and fibres - they give the cytoplasm physical support. Michael Kent, (2000) describes the cytoskeleton as the ‘internal framework’, this is because it shapes the cell and provides support to cellular extensions – such as microvilli. In some cells it is used in intracellular transport. Since the shape of the cell is constantly changing, the microtubules will also change, they will readjust and reassemble to fit the needs of the cell.

    Read More

  • Meiosis

    458 Words  | 1 Pages

    In prometaphase I, the nuclear membrane disappears. One kinetochore forms per chromosome , and the chromosomes attached to spindle fibers begin to move.

    Read More

  • Essay On Cilia

    948 Words  | 2 Pages

    All types of cilia have a length of about 10-15 μm and comprises of the same basic structure. A cilium is a microtubule-based organelle, which extends from a microtubule organizing chamber- the basal body, a centriole and at the apical surface of the cell bears microtubule cytoskeleton called the ciliary axoneme surrounded by a specialized ciliary membrane. The primary or the non-motile cilia consist of the ‘9+0’ arrangement of the axoneme, with the normal nine outer microtubule doublets and no central microtubule pair. Since the primary cilia are non-motile, therefore they usually lack dynein arms and radial spokes connected to the microtubule doublets. Primary cilia can receive signals from the extracellular biochemical and physical environments. Nodal cilia like primary cilia, occur solitary, having the 9+0 arrangement of axoneme, however, nodal cilia bears L, R...

    Read More

  • Cell Division Essay

    865 Words  | 2 Pages

    The process of cell division plays a very important role in the everyday life of human beings as well as all living organisms. If we did not have cell division, all living organisms would cease to reproduce and eventually perish because of it. Within cell division, there are some key roles that are known as nuclear division and cytokinesis. There are two types within nuclear division. Those two types being mitosis and meiosis. Mitosis and meiosis play a very important role in the everyday life as well. Mitosis is the asexual reproduction in which two cells divide in two in order to make duplicate cells. The cells have an equal number of chromosomes which will result in diploid cells. Mitosis is genetically identical and occurs in all living

    Read More

  • Mitochondria Essay

    1278 Words  | 3 Pages

    Cells are the basic building blocks of all living things. The human body is composed of trillions of cells. They provide structure for the body, take in nutrients from food, convert those nutrients into energy, and carry out specialized functions. But it also contains highly organized physical structures which are called intracellular organelles. These organelles are important for cellular function. For instance Mitochondria is the one of most important organelle of the cell. Without Mitochondria more than 95% of the cell’s energy, which release from nutrients would cease immediately [Guyton et al. 2007].

    Read More

  • Sex Determination and Differentiation

    656 Words  | 2 Pages

    Once the sperm fuses with the ovum both chromosomes will pair up and begin the first stages of cell division.

    Read More

  • Cell Cycle Essay

    1327 Words  | 3 Pages

    There are certain things that must happen first before the cell can actually split. There is a six step process required during Mitosis. The first five steps of mitosis are called prophase, prometaphase, metaphase, anaphase, and telophase. This is where all the training and preparation is done for cell division. The sixth step is Cytokinesis, and that is when the cell literally splits into two. Like I said, there are certain things in order to happen before it can enter the M phase. first, it must meet the requirements of the certain size and environment. Since in the S phase the cell duplicated it’s amount of chromosomes it be represented as 2N, where N equals the number of chromosomes in the cell. Cells about to enter M phase, which have passed through S phase and replicated their DNA, have 4N chromosomes. Because of this they are now allowed to enter within the M phase to prophase. Here is where the cell thickens up its chromosomes and begin to sprout microtubules from clone centrosomes. Microtubules tub-like are protein filaments and where the chromosomes migrate but are still within the nuclear envelope in the nucleus. There are centromeres, that are inside the chromosomes and during the later process of this phase, specialized microtubules called kinetochores, assemble on the centromere then later attach to these sites. They act like magnets and go

    Read More

More about Centrosomes Essay

Open Document