Biological Sciences
Mitotic Phase
The mitotic phase is a stage of the cell cycle during which a cell divides to produce two identical daughter cells. It consists of several subphases, including prophase, metaphase, anaphase, and telophase. During these subphases, the cell undergoes processes such as chromosome condensation, alignment of chromosomes at the cell's equator, separation of sister chromatids, and formation of new nuclear envelopes around the separated chromosomes.
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10 Key excerpts on "Mitotic Phase"
eBook - PDF- Rathoure, Ashok Kumar(Authors)
- 2021(Publication Date)
- Daya Publishing House(Publisher)
These events can be divided in two broad periods; interphase during which the cell grows, accumulating nutrients needed for mitosis and duplicating its DNA and the mitotic (M) phase, during which the cell splits itself into two distinct cells called daughter cells. The cell division cycle is an essential process by which a single celled fertilized egg develops into a mature organism, as well as the process by which hair, skin, blood cells and some internal organs are renewed. Phases of Cell Cycle The cell cycle consists of four distinct phases G 1 phase, S phase, G 2 phase (interphase) and M phase. M phase is itself composed of two tightly coupled processes i.e . mitosis, in which the cell’s chromosomes are divided between the two daughter cells and cytokinesis, in which the cell’s cytoplasm divides forming distinct cells. Activation of each phase is dependent on the proper 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 G 0 phase. This ebook is exclusively for this university only. Cannot be resold/distributed. Figure 4.1: Schematic of Cell cycle M phase: The relatively brief M phase consists of nuclear division (mitosis) and cytoplasmic division (cytokinesis). Interphase: After M phase, the daughter cells each begin interphase of a new cycle. Although the various stages of interphase are not usually morphologically distinguishable, each phase of cell cycle has a distinct set of specialized biochemical processes that prepare the cell for initiation of cell division. G 1 phase: The first phase within interphase, from the end of the previous This ebook is exclusively for this university only. Cannot be resold/distributed. M phase till the beginning of DNA synthesis is called G 1 (G indicating gap or growth). During this phase the biosynthetic activities of the cell, which had been considerably slowed down during M phase, resume at a high rate.
eBook - PDFKarp's Cell and Molecular Biology
Concepts and Experiments
- Gerald Karp, Janet Iwasa, Wallace Marshall(Authors)
- 2016(Publication Date)
- Wiley(Publisher)
Mitosis is a process of nuclear division in which the replicated DNA molecules of each chromosome are faithfully segregated into two nuclei. Mitosis is usually accompanied by cytokinesis, a process by which a dividing cell splits in two, partitioning the cytoplasm into two cellular packages. The two daughter 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, main- tains the chromosome number 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 gametophytes, 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, includ- ing transcription 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 263). 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, tubulin, 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 spontane- ously within the cell‐free mixture. In many experiments, the role of a particular protein in mitosis can be studied by removing that pro- tein from the egg extract by addition of an antibody (immunodeple- tion) and determining whether the process can continue in the absence of that substance (see Figure 14.21 for an example).
eBook - PDF- Ram J. Singh(Author)
- 2016(Publication Date)
- CRC Press(Publisher)
85 4 Cell Division 4.1 INTRODUCTION Cell division is a continuous process that occurs in all living organisms. It has been divided into two categories: mitosis and meiosis. Both forms of nuclear division occur in eukaryotes and these pro-cesses comprise the cell cycle: G 1 (growth) → S (synthesis of DNA) → G 2 (growth) → M (mitosis or meiosis) → C (cytokinesis) (Smith and Kindfield, 1999). Mitosis occurs in somatic tissues where each chromosome is divided identically into halves, both qualitatively and quantitatively, producing genetically identical to the parent nucleus. In contrast, meiosis takes place in germ cells with the consequence that nuclei with haploid chromosome numbers are produced. Both types of cell divi-sion play an important role in the development and hereditary continuity of a eukaryotic organism. 4.2 MITOSIS 4.2.1 P ROCESS OF M ITOSIS The term mitosis is derived from the Greek word mitos for thread; coined by Flemming in 1879 (see Chapter 1 ). The synonym of mitosis is karyokinesis, that is, the actual division of a nucleus into two identical parental daughter nuclei. It is also known as equational division because the exact longitudinal division of each chromosome into identical chromatids and their precise distribution into daughter nuclei leads to the formation of two cells; identical to the original cell from which they were derived. The process of mitotic cell division has been divided into six stages: (1) interphase, (2) prophase, (3) metaphase, (4) anaphase, (5) telophase, and (6) cytokinesis. 4.2.1.1 Interphase Two more terms, resting stage and metabolic stage, have been used to identify interphase cells. However, interphase cells should not be described as being in a “resting stage” because their nuclei are very active as they prepare for cell division. The DNA replication and transcription occur during interphase (Manuelidis, 1990).
eBook - ePub- Ram J. Singh(Author)
- 2016(Publication Date)
- CRC Press(Publisher)
4 Cell Division 4.1 INTRODUCTIONCell division is a continuous process that occurs in all living organisms. It has been divided into two categories: mitosis and meiosis. Both forms of nuclear division occur in eukaryotes and these processes comprise the cell cycle: G1 (growth) → S (synthesis of DNA) → G2 (growth) → M (mitosis or meiosis) → C (cytokinesis) (Smith and Kindfield, 1999). Mitosis occurs in somatic tissues where each chromosome is divided identically into halves, both qualitatively and quantitatively, producing genetically identical to the parent nucleus. In contrast, meiosis takes place in germ cells with the consequence that nuclei with haploid chromosome numbers are produced. Both types of cell division play an important role in the development and hereditary continuity of a eukaryotic organism.4.2 MITOSIS4.2.1 PROCESS OF MITOSISThe term mitosis is derived from the Greek word mitos for thread; coined by Flemming in 1879 (see Chapter 1 ). The synonym of mitosis is karyokinesis, that is, the actual division of a nucleus into two identical parental daughter nuclei. It is also known as equational division because the exact longitudinal division of each chromosome into identical chromatids and their precise distribution into daughter nuclei leads to the formation of two cells; identical to the original cell from which they were derived.The process of mitotic cell division has been divided into six stages: (1) interphase, (2) prophase, (3) metaphase, (4) anaphase, (5) telophase, and (6) cytokinesis. 4.2.1.1 InterphaseTwo more terms, resting stage and metabolic stage, have been used to identify interphase cells. However, interphase cells should not be described as being in a “resting stage” because their nuclei are very active as they prepare for cell division. The DNA replication and transcription occur during interphase (Manuelidis, 1990). Interphase consists of three phases: G1 (gap 1; pre-DNA synthesis) phase, S phase (DNA synthesis), and G2 (gap 2; post-DNA synthesis). The duration of mitotic division is short compared to time required for the cells going through interphase (Figure 4.1 ). Thus, “metabolic stage” is a more appropriate term for the interphase cells. The interphase nucleus contains one or more prominent nucleoli and numerous chromocenters depending on the heterochromatic nature of the chromosomes. Chromosomes cannot be traced individually and they are very lightly stained (Figure 4.2a
eBook - PDF- Gerald Karp, Janet Iwasa, Wallace Marshall(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
Mitosis, therefore, maintains the chromosome number 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 gametophytes, 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 transcription and translation, are largely curtailed during mitosis, and the cell becomes relatively unre- sponsive to external stimuli. You 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 (Section 8.2). 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 of the materials (histones, tubulin, 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. In many experiments, the role of a particu- lar protein in mitosis can be studied by removing that protein from the egg extract by addition of an antibody (immunodeple- tion) and determining whether the process can continue in the absence of that substance (see Figure 14.21 for an example). Mitosis is generally divided into five stages (Figure 14.11): prophase, prometaphase, metaphase, anaphase, and telo- phase, each characterized by a particular series of events. Keep in mind that each of these stages represents a segment of a con- tinuous process; the division of mitosis into arbitrary phases is done only for the sake of discussion and experimentation.
eBook - PDFCells and Tissues in Culture
Methods, Biology and Physiology
- E. N. Willmer(Author)
- 2015(Publication Date)
- Academic Press(Publisher)
II. MITOSIS A. GENERAL SURVEY 1. Definition of Phases It is not necessary here to give again at length the classical description of mitosis, familiar to every reader. Observation of living cells by phase-contrast has brought about a habit of subdividing mitosis into 5 phases, separated by sudden morphological changes—not always so easy to identify on fixed cells—rather than the old-time 4 stages. It is useful to determine the overall duration and that of each phase * for each type of cell used and for each method of culture. This determination is essential in any study of mitotic poisons which may alter them and it conditions the relative frequency of phases in fixed and stained prepara-tions. The biochemical events, still largely unexplored, underlying cell division may not begin and end at the same moments as the morpho-logical phenomena. But the latter furnish us with a convenient time sequence. *This already interested W. Fleming in 1882. 6. CELL DIVISION 205 In vertebrate cultures, prophase has an imprecise beginning. It starts perhaps by a rotation of the nucleus (Commandon, de Fonbrunne and Jolly, 1934; Hughes, 1952) happening too early to be caught often by the cine camera. The chromosomes as seen with phase contrast become more and more distinct but remain inside the nuclear envelope. Prophase ends by the sudden fading of the nucleolus and disappearance of the nuclear membrane. Prometaphase is a variable period. The chromosomes spread slowly out of the former nuclear area and attach themselves one by one to the spindle. Characteristic to and fro move-ments of the chromosomes continue until they are all attached. Then, suddenly, the group freezes into an equatorial plate. This is the metaphase proper, usually short and sometimes coinciding with the beginning of peripheral cytoplasmic ''bubbling. The onset of anaphase, when the chromosomes begin to draw apart, is a sharply defined event, perhaps the most dramatic moment of the division.
eBook - ePub- Julia E. Richards, R. Scott Hawley(Authors)
- 2010(Publication Date)
- Academic Press(Publisher)
During the next step, S, DNA synthesis copies the chromosomes. During G2, the cell finishes off any remaining metabolic processes needed for cell division. Interphase consists of G1 plus S plus G2, a period during which the cell looks pretty much the same under the microscope. The microscopic view starts to change during M phase, or mitosis, when the chromosomes condense (prophase), line up (metaphase), move to the separate ends of the dividing cell (anaphase), and then are packaged back into a nucleus as the cell prepares to divide (telophase) in an orderly manner. Cytokinesis divides the cell into the two new daughter cells. Cells that are growing slowly spend a lot of time in G1. This pie chart shows an average representation of amount of time in the cell cycle spent in each of these stages. It also shows that mitosis is a very brief part of the cell cycle. If cells are truly inactive and not dividing, they go into a metabolic resting state called G0 instead of going into G1. Take-home message: During interphase, when the nucleus looks like a Brillo pad, the cell makes copies of everything and gets ready for cell division. During the visibly distinct stages of mitosis, the cell carts the chromosomes around to where they should be (a process we can see under the microscope), and cytokinesis completes the separation into two cells. Through most of the cell’s life the DNA molecules are loosely entwined with each other in the cell nucleus, going about the gentle business of running various aspects of metabolism and growth through transcription of genes to produce functional gene products. During this time, the chromosomes are not visible as separate entities; rather, the nucleus looks like an old Brillo pad. Only once the cell starts the process of mitosis do we begin to see distinct structures within the nucleus. So let’s take a look at mitosis and see how it works. 6.2
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- John H. Lawrence, Cornelius A. Tobias, John H. Lawrence, Cornelius A. Tobias(Authors)
- 2013(Publication Date)
- Academic Press(Publisher)
The situation in bacteria remains unresolved. Bodies staining like chromosomes and aligning themselves in the dividing cell in arrangements similar to mitotic figures have been described by DeLamater and others (25, 26), working with painstaking techniques at the very limits of resolution of the light microscope. These observations have not gone unchallenged (6). It is now established in a considerable number of cases that the actual duplication of the chromosomes takes place between divisions or, at the latest, early in the prophase (40, 109, 113). Therefore, the essential fea-ture of mitosis is the separation of the daughters produced by the duplica-tion of a set of chromosomes in such a way that one of each pair of daughters goes to each daughter nucleus. In the typical plant and animal case, the nuclear membrane disappears, and the process of separating 72 DANIEL MAZIA TABLE I Major Variations of the Scheme of Cell Division I. Mitosis leading to the formation of separate daughter nuclei. A. Nuclear behavior during prophase. 1. Nuclear membrane disappears (most plants and animals). 2. Nuclear membrane persists through division (many protozoa, some animals). B. Chromosome alignment at metaphase. 1. All of chromosomes contained in metaphase plate (many large cells with small chromosomes). 2. Kinetochores (centromeres) only aligned on equatorial plane. Arms of chromosomes dangle from equatorial plane (many small cells with large chromosomes). 3. Equatorial alignment not evident. Chromosomes may lie entirely outside continuous spindle, connected to poles by chromosomal fibers. Metaphase plate may lie obliquely to axis of spindle (pollen tubes). C. Spindle form. 1. Continuous spindle fibers from pole to pole intermingled with chromosomal fibers connecting chromosomes to poles (many plant and animal cells). 2. Continuous central spindle may be distinct from half spindles con-necting chromosomes to poles.
eBook - PDF- Julianne Zedalis, John Eggebrecht(Authors)
- 2018(Publication Date)
- Openstax(Publisher)
cell, nucleus, or organism containing two sets of chromosomes (2n) tubulin-like protein component of the prokaryotic cytoskeleton that is important in prokaryotic cytokinesis (name origin: Filamenting temperature-sensitive mutant Z) distinct from the G 1 phase of interphase; a cell in G 0 is not preparing to divide (also, first gap) first phase of interphase centered on cell growth during mitosis (also, second gap) third phase of interphase during which the cell undergoes final preparations for mitosis haploid reproductive cell or sex cell (sperm, pollen grain, or egg) physical and functional unit of heredity, a sequence of DNA that codes for a protein. total genetic information of a cell or organism cell, nucleus, or organism containing one set of chromosomes (n) one of several similar, highly conserved, low molecular weight, basic proteins found in the chromatin of all eukaryotic cells; associates with DNA to form nucleosomes chromosomes of the same morphology with genes in the same location; diploid organisms have pairs of homologous chromosomes (homologs), with each homolog derived from a different parent period of the cell cycle leading up to mitosis; includes G 1 , S, and G 2 phases (the interim period between two consecutive cell divisions mitotic nuclear division 434 Chapter 10 | Cell Reproduction This OpenStax book is available for free at http://cnx.org/content/col12078/1.6
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