 Show The Biology Project > Cell Biology > Intro. to Cell Cycle & Mitosis > Tutorial MitosisWhat is (and is not) mitosis?Mitosis is nuclear division plus cytokinesis, and produces two identical daughter cells during prophase, prometaphase, metaphase, anaphase, and telophase. Interphase is often included in discussions of mitosis, but interphase is technically not part of mitosis, but rather encompasses stages G1, S, and G2 of the cell cycle. Interphase & mitosis
Previous | Next Vocabulary The Biology Project > Cell Biology > Intro. to Cell Cycle & Mitosis > Tutorial http://www.biology.arizona.edu In this electron micrograph of a cell, the cleavage furrow has nearly completely divided the cell. Cilliate undergoing the last processes of binary fission, with the cleavage furrow being clearly visible. In cell biology, the cleavage furrow is the indentation of the cell's surface that begins the progression of cleavage, by which animal and some algal cells undergo cytokinesis, the final splitting of the membrane, in the process of cell division. The same proteins responsible for muscle contraction, actin and myosin, begin the process of forming the cleavage furrow, creating an actomyosin ring. Other cytoskeletal proteins and actin binding proteins are involved in the procedure. Mechanism[edit]Plant cells do not perform cytokinesis through this exact method but the two procedures are not totally different. Animal cells form an actin-myosin contractile ring within the equatorial region of the cell membrane that constricts to form the cleavage furrow.[1] In plant cells, Golgi vesicle secretions form a cell plate or septum on the equatorial plane of the cell wall by the action of microtubules of the phragmoplast.[2] The cleavage furrow in animal cells and the phragmoplast in plant cells are complex structures made up of microtubules and microfilaments that aide in the final separation of the cells into two identical daughter cells. Cell cycle[edit]The cell cycle begins with interphase when the DNA replicates, the cell grows and prepares to enter mitosis. Mitosis includes four phases, prophase, metaphase, anaphase, and telophase. Prophase is the initial phase when spindle fibers appear that function to move the chromosomes toward opposite poles. This spindle apparatus consists of microtubules, microfilaments and a complex network of various proteins. During metaphase, the chromosomes line up using the spindle apparatus in the middle of the cell along the equatorial plate. The chromosomes move to opposite poles during anaphase and remain attached to the spindle fibers by their centromeres. Animal cell cleavage furrow formation is caused by a ring of actin microfilaments called the contractile ring, which forms during early anaphase. Myosin is present in the region of the contractile ring as concentrated microfilaments and actin filaments are predominant in this region. The actin filaments here are both pre-existing and new. Cleavage is driven by these motor proteins, actin and myosin, which are the same proteins involved with muscle contraction. During cellular cleavage, the contractile ring tightens around the cytoplasm of the cell until the cytoplasm is pinched into two daughter cells. During the final phase of mitosis, telophase, the furrow forms an intercellular bridge using mitotic spindle fibers. Phosphatidylethanolamine (PE) has been shown to be present during this time which indicates that is may play a role in movement between the plasma membrane and contractile ring.[3] The bridge is then broken and resealed to form two identical daughter cells during cytokinesis. The breakage is formed by microtubules and the resealing is negated by Calcium dependent exocytosis using Golgi vesicles.[2] In comparison, the plant cell septum and the animal cell mid-zone are analogous. Both require vesicular secretions by the Golgi apparatus for resealing and formation of the cytoskeletal network in addition to microtubules and microfilaments for division and movement.[4] The cleavage furrow mechanism in animal cells is a complex network of actin and myosin filaments, Golgi vesicles and Calcium dependent channels enabling the cell to break apart, reseal and form new daughter cells with complete membranes.[2] References[edit]
What is it called when animal cells begin to pinch into two cells in telophase?Cytokinesis is the physical process of cell division, which divides the cytoplasm of a parental cell into two daughter cells. It occurs concurrently with two types of nuclear division called mitosis and meiosis, which occur in animal cells.
What is the indentation in telophase?Cleavage Furrow. At the same time, there is a division of the cytoplasm (cytokinesis). In animal cells, a cleavage furrow — an indentation around the equator of the cell — appears (see photo left). By the end of telophase, the cell has divided in two along the plane defined by the furrow.
What is it called when the cytoplasm pinches in during telophase?Cytokinesis is the final stage in the cell cycle. The cytoplasm pinches in half and separates the nuclei into two daughter cells.
What is it called when the cell membrane pinches?Cytokinesis is the physical process that finally splits the parent cell into two identical daughter cells. During cytokinesis, the cell membrane pinches in at the cell equator, forming a cleft called the cleavage furrow.
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