Biological Sciences
Cytokinesis
Cytokinesis is the process by which a cell divides its cytoplasm to form two daughter cells following nuclear division. It involves the physical separation of the cytoplasmic components, including organelles and cytosol, to ensure that each daughter cell receives a complete set of cellular machinery. Cytokinesis is a crucial step in the cell cycle and is essential for the growth and development of organisms.
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eBook - PDFKarp's Cell and Molecular Biology
Concepts and Experiments
- Gerald Karp, Janet Iwasa, Wallace Marshall(Authors)
- 2016(Publication Date)
- Wiley(Publisher)
Cytokinesis Mitosis accomplishes the segregation of duplicated chromosomes into daughter nuclei, but the cell is divided into two daughter cells by a separate process called Cytokinesis. The first hint of Cytokinesis in most animal cells appears during anaphase as an indentation of the cell surface in a narrow band around the cell. As time progresses, the indentation deepens to form a furrow that moves inward toward the center of the cell. The plane of the furrow lies in the same plane previously occupied by the chromosomes of the metaphase plate, so that the two sets of chromosomes are ultimately partitioned into dif- ferent cells (as in Figure 14.32). As one cell becomes two cells, addi- tional plasma membrane is delivered to the cell surface via cytoplasmic vesicles that fuse with the advancing cleavage furrow. In its latter stages, the advancing furrow passes through the tightly CHAPTER 14 • Cell Division 568 packed remnants of the central portion of the mitotic spindle, which forms a cytoplasmic bridge between the daughter cells called the midbody (FIGURE 14.34a ). The final step of Cytokinesis is called abscission, when the surfaces of the cleavage furrow fuse with one another, splitting the cell in two (Figure 14.34 b). Abscission requires the action of ESCRT complexes—the same proteins responsible for severing the intraluminal vesicles that form within endosomes (page 301). Our present concept of the mechanism responsible for cytoki- nesis stems from a proposal made by Douglas Marsland in the 1950s known as the contractile ring theory (FIGURE 14.35a). Marsland pro- posed that the force required to cleave a cell is generated in a thin band of contractile cytoplasm located in the cortex, just beneath the plasma membrane of the furrow. Microscopic examination of the cortex beneath the furrow of a cleaving cell reveals the presence of large numbers of actin filaments (Figure 14.35 b and 14.36 a).
eBook - PDFHuman Heredity
Principles and Issues
- Michael Cummings(Author)
- 2015(Publication Date)
- Cengage Learning EMEA(Publisher)
As they continue to condense, they are seen as double structures, with sister chromatids joined at a single centromere. Metaphase Chromosomes become aligned at equator of cell. Anaphase Centromeres divide, and chromosomes move toward opposite poles. Telophase Chromosomes decondense; nuclear membrane forms. Jennifer C. Waters/Science Source Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. 30 Chapter 2 Cytokinesis divides the cytoplasm. Although the molecular events that underlie Cytokinesis begin during mitosis, the first visible sign of Cytokinesis is the formation of a constriction called a cleav-age furrow at the equator of the cell ( Figure 2.11 ). In many cell types, this furrow forms in late anaphase or telophase. The constriction gradually tightens by the contraction of filaments just under the plasma membrane, and the cell eventually divides in two, distributing organelles to the daughter cells. 2-5 Mitosis Is Essential for Growth and Cell Replacement Mitosis is an essential process in humans and all multicellular organisms. Some cells retain the capacity to divide throughout their life cycle, whereas others do not divide in adulthood. For example, cells in bone marrow continually move through the cell cycle, producing about 2 million red blood cells each second. Skin cells constantly divide to replace dead cells that are sloughed off the surface of the body. By contrast, other cells, including many cells in the nervous system, leave the cell cycle, enter G0, and do not divide in adulthood.
eBook - PDF- Gerald Karp, Janet Iwasa, Wallace Marshall(Authors)
- 2018(Publication Date)
- Wiley(Publisher)
The beauty and precision of cell division is best appreciated by watching a time‐lapse video of the process (e.g., www.bio.unc.edu/faculty/salmon/lab/mitosis/mitosismovies. html) rather than reading about it in a textbook. Mitosis is a process of nuclear division in which the repli- cated DNA molecules of each chromosome are faithfully segre- gated into two nuclei. Mitosis is usually accompanied by Cytokinesis, a process by which a dividing cell splits in two, parti- tioning the cytoplasm into two cellular packages. The two daugh- ter cells resulting from mitosis and Cytokinesis possess a genetic content identical to each other and to the mother cell from which they arose. Mitosis, therefore, maintains the chromosome num- ber and generates new cells for the growth and maintenance of an organism. Mitosis can take place in either haploid or diploid cells. Haploid mitotic cells are found in fungi, plant gameto- phytes, and a few animals (including male bees known as drones). Mitosis is a stage of the cell cycle when the cell devotes virtually all of its energy to a single activity—chromosome segregation. As a result, most metabolic activities of the cell, including transcrip- tion and translation, are curtailed during mitosis, and the cell becomes relatively unresponsive to external stimuli. We have seen in previous chapters how much can be learned about the factors responsible for a particular process by studying that process outside of a living cell (page 469). Our understanding of the biochemistry of mitosis has been greatly aided by the use of extracts prepared from frog eggs. These extracts contain stockpiles of all the materials (histones, tubu- lin, etc.) necessary to support mitosis. When chromatin or whole nuclei are added to the egg extract, the chromatin is compacted into mitotic chromosomes, which are segregated by a mitotic spindle that assembles spontaneously within the cell‐ free mixture.
eBook - PDF- Emea, A(Authors)
- 2018(Publication Date)
- Agri Horti Press(Publisher)
Cell Divisions 1 C HAPTER 1 Cell Divisions Cell division is the process that cells go through in order to divide. Cells may divide for several reasons, and there are two types of cell division depending on the purpose. The cell division associated with sexual reproduction is one type, called meiosis. The other type, the cell division associated with growth and cell replacement or repair, is called mitosis. In both types of cell division, the nucleus splits and DNA is replicated. The cell division called mitosis produces daughter cells that have all the genetic material of the parent cell — a complete set of chromosomes. However, chromosomes are not the only material that needs to be divided and transferred to the daughter cells: there are cytoplasm and the cell membrane to divide as well. Cytokinesis is the process of dividing the cytoplasm and the cell membrane, and this process may follow immediately after mitosis or occur separately, depending on the organism involved. Together, these two processes make up the mitotic phases of the cell cycle. The phases of cell division are prophase, metaphase, anaphase, and telophase, and these occur in both mitosis and meiosis. A fifth phases called prometaphase occurring between prophase and metaphase is designated by some, but not all sources. Interphase, which is not part of mitosis, is a preparatory stage during which the parent cell makes a copy of its genetic material so that each daughter cell can have a complete set. Therefore, mitosis is an ongoing and repetitive process, alternating with interphase. Cell division is the complex phenomenon by which cellular material is divided equally between daughter cells. This process is the final, and microscopically visible, phase of an underlying change that has occurred at molecular and biochemical levels. Before the cell divides by mitosis, its fundamental components have duplicated-particularly those involved in hereditary transmission.
eBook - PDF- Arthur Zimmerman(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
INTRODUCTION The aim of research on Cytokinesis, as in many other areas of biology, is to understand the nature of the process at the molecular level and the mechanisms which regulate its onset and progress. As may be seen from Chapter 16 by Conrad and Rappaport in this volume, Cytokinesis has been studied in a number of different cells using a variety of methodologies. One approach commonly used to try to understand biological processes, particu-larly in systems where one cannot work with isolated and purified material, is to treat the living cell with selected agents and observe how the process of interest responds to the treatment. What is learned from such studies is a function of a number of factors, especially the specificity of the perturbing agent. Ideally, an agent should react only with a single, well-characterized molecule which is directly and uniquely involved in the process of interest, and its effects should be easily measured. In general, and specifically in the case of Cytokinesis, the agents available frequently either lack the desired specificity or their specificities are as yet 437 MITOSIS/Cytokinesis Copyright © 1981 by Academic Press, Inc. All rights of reproduction in any form reserved. ISBN 0-12-781240-7 438 Jesse E. Sisken unknown. In addition, it is often difficult to distinguish between primary and secondary effects. Nevertheless, the judicious use of various types of agents can be instructive, and in this chapter I will discuss what I believe to be representative examples from the literature and from my own laboratory to illustrate some of the work that has been done in studying Cytokinesis with this approach. The objective will be to evaluate the approach and not to review our knowledge of Cytokinesis; this has been done elsewhere in this volume.
eBook - PDFCells and Tissues in Culture
Methods, Biology and Physiology
- E. N. Willmer(Author)
- 2015(Publication Date)
- Academic Press(Publisher)
Each of them is visible for 15-40 sec (Hughes, 1952). Boss (1955) suggests that they appear particularly in areas where the RNA concentration is high. Sometimes the proximity of a chromosome to the cell surface seems to favour a repeated local bubbling. In cultured cells, Cytokinesis seems less dependent on the position of the spindle and the separation of chromosomes than in other materials where the achromatic apparatus is bigger. The cytoplasm tends to cleave in two whether the nuclear phenomena have reached their normal conclusion or not. This has been observed in individual cases after blocking of the spindle by beryllium or other substances (Chevremont and Firket, 1952a). Under the influence of diethyl-stilboestrol and testosterone (Lettre and Siebs, 1956) or a-particle irradiation of the spindle (Davis and Smith, 1957) sometimes chromo-somes are not separated, but cytoplasmic cleavage is normal and gives rise to a nucleated and an anucleated fragment of cytoplasm. Cytokinesis is usually mechanically prevented when a single large nucleus has reformed because of failure of anaphase (adenine; beryl-lium, etc.) but it can take place (for example after trypaflavine or irradiation) when a chromosome bridge links the two groups. In this case, the two daughter cells do not separate, but die together in pycnosis. Cytokinesis is dependent on an intact respiratory mechanism as shown by its frequent failure after a normal or quasi-normal division, when the cells are subjected to anaerobiosis (S. Chevremont and Frederic, 1955) cyanide (Chevremont and Firket, 1950), or cysteamine 216 H . F I R K E T FIG 7. Phase contrast photograph of a binucleate cell in a chick fibroblast culture treated with lithium chloride. This cell had been under observation for several hours. After normal anaphasic movements of the chromosomes, two nuclei reconstructed at opposite ends of the cell. The cytoplasm did not divide and the nuclei have come back towards the centre, x 1200.
eBook - PDF- Gerald Karp, Janet Iwasa, Wallace Marshall(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
638 CHAPTER 14 Cell Division 14.1 The Cell Cycle The process by which new cells arise from other living cells is called cell division. For a multicellular organism, such as a human or an oak tree, countless divisions of a single-celled zygote produce an organism of astonishing cellular complexity and organization. Cell division does not stop with the forma- tion of the mature organism but continues in certain tissues throughout life. Millions of cells residing within the marrow of your bones or the lining of your intestinal tract are undergoing division at this very moment. This enormous output of cells is needed to replace cells that have aged or died. Although cell division occurs in all organisms, it takes place very differently in prokaryotes and eukaryotes. We restrict dis- cussion to the eukaryotic version. Two distinct types of eukary- otic cell division are discussed in this chapter. Mitosis leads to production of cells that are genetically identical to the parent, whereas meiosis leads to production of cells with half the genetic content of the parent. Mitosis serves as the basis for producing new cells, and meiosis is the basis for producing new sexually reproducing organisms. Together, these two types of cell division form the links in the chain between parents and their offspring and, in a broader sense, between living species and the earliest eukaryotic life forms present on Earth. Phases of the Cell Cycle In a population of dividing cells, whether inside the body or in a culture dish, each cell passes through a series of defined stages, which constitutes the cell cycle (Figure 14.1). The cell cycle can be divided into two major phases based on cellular activities readily visible with a light microscope: M phase and interphase. M phase includes (1) the process of mitosis, during which duplicated chromosomes are separated into two nuclei, and (2) Cytokinesis, during which the entire cell divides into two daughter cells.
eBook - PDF- John H. Lawrence, Cornelius A. Tobias, John H. Lawrence, Cornelius A. Tobias(Authors)
- 2013(Publication Date)
- Academic Press(Publisher)
Cytokinesis: Division of the Cell Body 110 VII. The Interpretation of Experiments with Antimitotic Agents 112 References 115 69 70 DANIEL MAZIA I. THE PROBLEM OF CELL DIVISION—INTRODUCTION The problem of cell division is recognized so generally as an important one that it is difficult to speak of its importance without falling into platitudes. It is even more difficult to account for the fact that relatively little research is being done on cell division at this time, but the simplest explanation is that it is considered too complex a problem to attack by the more attractive experimental methods. Even if this were the case— and much in the following paper will demonstrate that it is not—it can be assumed that sooner or later the full weight of modern experimental attack will be turned on cell division as it has been turned on other problems. The following essay is an attempt to condense the informational background required for a biophysical and biochemical approach to the problem. It is not a complete review of the literature. What is attempted is an integration of old and new information with two ends in mind: first, to seek out uniformities where they exist and to point out variation where it seems to vitiate generalization; second, to point up problems that are yielding to biophysical and biochemical attack or at least can now be formulated in such terms. Obviously, what we are seeking at this stage are intelligible mechanisms to explain the complex events of cell division. I stress intelligibility rather than simplicity because the past history of this field contains so many instances in which simple physical models have had mischievous consequences. There have appeared in recent years a number of important reviews covering various aspects of cell division, notably those of Schräder (95), Hughes (45), and Ris (89). See also note added in proof, p. 118. It is a consequence of the cell theory that the growth of a biological system is a discontinuous process.
eBook - PDF- William V Dashek, Marcia Harrison(Authors)
- 2010(Publication Date)
- CRC Press(Publisher)
• The total DNA of a cell, consisting of at least one chromosome, is called the genome. Cell Division Cell division involves division of both the nucleus and the cell cytoplasm. • Mitosis and meiosis are the pro- cesses by which the nucleus divides. • Cytokinesis is the process whereby the cytoplasm is divided into two new daughter cells. • Mitosis results in two daughter nuclei with the same number of chromosomes and an amount of genetic material identical to the parent cell. Mitosis generates numerous cells and these build the body of the plant. • Meiosis produces daughter cells that each have half the amount of genetic material of the parent cell. For this reason meiosis is called a "reduction division". Meiosis pro- duces reproductive cells, called gametes, eggs, and sperm. 222 PLANT CELL BIOLOGY MITOSIS IN PLANT CELLS 223 • Cytokinesis divides the cell cytoplasm, and each daughter cell then contains a nucleus as well as its share of mitochondria, chloro- plasts, and vacuoles. A new cell wall is synthesised between the two new daughter cells. Cell Cycle in Plants Cell division is only part of the life-cycle of cells. The life-cycle of cells is called the cell cycle. • The cell cycle consists of cell divi- sion, when the cell is occupied with dividing, and interphase, when the cell carries out its functions in the plant body, grows and increases in volume, and prepares for the next cell division. • The cell cycle is called a cycle because the cells pass through vari- ous phases and then the cycle starts again. • Duration of the cell cycle varies in different parts of the plant and in different cells. Meristematic cells of plants divide once every 18 to 24 hours, and the actual process of division takes 4 to 6 hours. • The cell cycle has five phases that flow smoothly into one another. • The phases can be diagrammed as Gl -> S -»G2 -> M -> C. • Phases Gl -» S -> G2 are together called interphase because they lie between cell divisions.
eBook - PDFMolecular Cytology V1
The Cell Cycle
- Jean Brachet(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
CHAPTER 5 CELL DIVISION I. GENERAL BACKGROUND There are two characteristics of cell division that sharply distinguish living organisms from nonliving machines: reproduction and heredity. When cells di-vide, the two daughter cells have the same heredity because they have received identical DNA molecules (both in amount and in sequence organization). In culture, they will give rise to identical strains until mutations and DNA rear-rangements induce the inevitable diversification that characterizes all living organisms. Finally, cell division remains the only method of reproduction for all asexual organisms. Sexual reproduction will be touched upon when we discuss oocytes and eggs in Volume 2, Chapter 2. In Biochemical Cytology, Chapter 5 was entitled Mitosis, not Cell Division. This change is due to the fact that, in 1957, little was known of the existence of a cell cycle. Although this idea had been proposed as early as 1953 by Howard and Pelc, it had little immediate impact on cytological research and thinking. The progress in this field in the years that followed was the subject of a book by Prescott (1976); a review by Hochhauser et al. (1981) includes about 1200 references on the subject. Today we know that the cell prepares for mitotic division by a series of complex events that ultimately lead to a revolution: mitosis, which produces two (in theory, at least) genetically identical daughter cells. We may call this a revolution because it is accompanied by a complete rearrangement of almost all of the cell constituents that have been considered so far. The preparatory events that culminate in mitosis are dominated by DNA replication. This phase of DNA synthesis (Fig. 1) is called the S phase of the cell cycle. Prior to DNA synthesis is the G! phase, which lasts for a variable length of time (it is even absent during the cleavage of fertilized eggs in most animal species).
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