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    early in mitosis, the nucleus, nucleolus, and nuclear envelope begin to dissolve in preparation for cell division. in which stage of the cell cycle is this process reversed?

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    get early in mitosis, the nucleus, nucleolus, and nuclear envelope begin to dissolve in preparation for cell division. in which stage of the cell cycle is this process reversed? from EN Bilgi.

    The Nucleus during Mitosis

    A unique feature of the nucleus is that it disassembles and re-forms each time most cells divide. At the beginning of mitosis, the chromosomes condense, the nucleolus disappears, and the nuclear envelope breaks down, resulting in the release of most of the contents of the nucleus into the cytoplasm. At the end of mitosis, the process is reversed: The chromosomes decondense, and nuclear envelopes re-form around the separated sets of daughter chromosomes. Chapter 14 presents a comprehensive discussion of mitosis; in this section we will consider the mechanisms involved in the disassembly and re-formation of the nucleus. The process is controlled largely by reversible phosphorylation and dephosphorylation of nuclear proteins resulting from the action of the Cdc2 protein kinase, which is a critical regulator of mitosis in all eukaryotic cells.

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    The Cell: A Molecular Approach. 2nd edition.

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    The Nucleus during Mitosis

    A unique feature of the nucleus is that it disassembles and re-forms each time most cells divide. At the beginning of mitosis, the chromosomes condense, the nucleolus disappears, and the nuclear envelope breaks down, resulting in the release of most of the contents of the nucleus into the cytoplasm. At the end of mitosis, the process is reversed: The chromosomes decondense, and nuclear envelopes re-form around the separated sets of daughter chromosomes. Chapter 14 presents a comprehensive discussion of mitosis; in this section we will consider the mechanisms involved in the disassembly and re-formation of the nucleus. The process is controlled largely by reversible phosphorylation and dephosphorylation of nuclear proteins resulting from the action of the Cdc2 protein kinase, which is a critical regulator of mitosis in all eukaryotic cells.

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    Dissolution of the Nuclear Envelope

    In most cells, the disassembly of the nuclear envelope marks the end of the prophase of mitosis (Figure 8.29). However, this disassembly of the nucleus is not a universal feature of mitosis and does not occur in all cells. Some unicellular eukaryotes (e.g., yeasts) undergo so-called closed mitosis, in which the nuclear envelope remains intact (Figure 8.30). In closed mitosis, the daughter chromosomes migrate to opposite poles of the nucleus, which then divides in two. The cells of higher eukaryotes, however, usually undergo open mitosis, which is characterized by breakdown of the nuclear envelope. The daughter chromosomes then migrate to opposite poles of the mitotic spindle, and new nuclei reassemble around them.

    Figure 8.29

    The nucleus during mitosis. Micrographs illustrating the progressive stages of mitosis in a plant cell. During prophase, the chromosomes condense, the nucleolus disappears, and the nuclear envelope breaks down. At metaphase, the condensed chromosomes (more...)

    Figure 8.30

    Closed and open mitosis. In closed mitosis, the nuclear envelope remains intact and chromosomes migrate to opposite poles of a spindle within the nucleus. In open mitosis, the nuclear envelope breaks down and then re-forms around the two sets of separated (more...)

    Disassembly of the nuclear envelope, which parallels a similar breakdown of the endoplasmic reticulum, involves changes in all three of its components: The nuclear membranes are fragmented into vesicles, the nuclear pore complexes dissociate, and the nuclear lamina depolymerizes. The best understood of these events is depolymerization of the nuclear lamina—the meshwork of filaments underlying the nuclear membrane. The nuclear lamina is composed of fibrous proteins, lamins, which associate with each other to form filaments. Disassembly of the nuclear lamina results from phosphorylation of the lamins, which causes the filaments to break down into individual lamin dimers (Figure 8.31). Phosphorylation of the lamins is catalyzed by the Cdc2 protein kinase, which was introduced in Chapter 7 (see Figure 7.40) and will be discussed in detail in Chapter 14 as a central regulator of mitosis. Cdc2 (as well as other protein kinases activated in mitotic cells) phosphorylates all the different types of lamins, and treatment of isolated nuclei with Cdc2 has been shown to be sufficient to induce depolymerization of the nuclear lamina. Moreover, the requirement for lamin phosphorylation in the breakdown of the nuclear lamina has been demonstrated directly by the construction of mutant lamins that can no longer be phosphorylated. When genes encoding these mutant lamins were introduced into cells, their expression was found to block normal breakdown of the nuclear lamina as the cells entered mitosis.

    Figure 8.31

    Dissolution of the nuclear lamina. The nuclear lamina consists of a meshwork of lamin filaments. At mitosis, Cdc2 and other protein kinases phosphorylate the lamins, causing the filaments to dissociate into free lamin dimers.

    In concert with dissolution of the nuclear lamina, the nuclear membrane fragments into vesicles (Figure 8.32). The B-type lamins remain associated with these vesicles, but lamins A and C dissociate from the nuclear membrane and are released as free dimers in the cytosol. This difference arises because the B-type lamins are permanently modified by the addition of lipid (prenyl groups), whereas the C-terminal prenyl groups of A- and C-type lamins are removed by proteolysis following their incorporation into the lamina. The nuclear pore complexes also dissociate into subunits as a result of phosphorylation of several nuclear pore proteins. Integral nuclear membrane proteins are also phosphorylated at mitosis, and phosphorylation of these proteins may be important in vesicle formation as well as in dissociation of the nuclear membrane from both chromosomes and the nuclear lamina.

    Source : www.ncbi.nlm.nih.gov

    [Expert Verified] Early in mitosis, the nucleus, nucleolus, and nuclear envelope begin to dissolve in

    Answer:The correct answer would be telophase.Telophase is the last phase of the mitotic phase. During this phase, the events took place prophase are usually rev…

    Unlock all answers 01/04/2015 Biology High School

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    Early in mitosis, the nucleus, nucleolus, and nuclear envelope begin to dissolve in preparation for cell division. In which stage of the cell cycle is this process reversed? cytokinesis interphase anaphase telophase

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    Answer Expert Verified

    5.0/5 198 Answer:

    The correct answer would be telophase.

    Telophase is the last phase of the mitotic phase.

    During this phase, the events took place prophase are usually reversed.

    Chromosomes reach the terminal ends of the dividing cell.

    New nuclear membrane forms around each daughter nuclei.

    Nucleoli also reappear.

    Chromosomes unfold or decondensed back to form chromatin.

    Cell continues to elongate which is followed by cytokinesis.

    Hence, telophase is the stage of cell cycle in which the mentioned events are reversed.

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    tramwayniceix and 282 more users found this answer helpful

    5.0 (84 votes)

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    4.8/5 105

    Answer:

    the answer is D telophase on edg 2020

    Explanation:

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    The Cell Cycle – Concepts of Biology

    THE CELL CYCLE

    Learning Objectives

    By the end of this section, you will be able to:

    Describe the three stages of interphase

    Discuss the behavior of chromosomes during mitosis and how the cytoplasmic content divides during cytokinesis

    Define the quiescent G0 phase

    Explain how the three internal control checkpoints occur at the end of G1, at the G2–M transition, and during metaphase

    The cell cycle is an ordered series of events involving cell growth and cell division that produces two new daughter cells. Cells on the path to cell division proceed through a series of precisely timed and carefully regulated stages of growth, DNA replication, and division that produce two genetically identical cells. The cell cycle has two major phases: interphase and the mitotic phase ([Figure 1]). During interphase, the cell grows and DNA is replicated. During the mitotic phase, the replicated DNA and cytoplasmic contents are separated and the cell divides.

    Watch this video about the cell cycle: https://www.youtube.com/watch?v=Wy3N5NCZBHQ

    Figure 1: A cell moves through a series of phases in an orderly manner. During interphase, G1 involves cell growth and protein synthesis, the S phase involves DNA replication and the replication of the centrosome, and G2 involves further growth and protein synthesis. The mitotic phase follows interphase. Mitosis is nuclear division during which duplicated chromosomes are segregated and distributed into daughter nuclei. Usually the cell will divide after mitosis in a process called cytokinesis in which the cytoplasm is divided and two daughter cells are formed.

    INTERPHASE

    During interphase, the cell undergoes normal processes while also preparing for cell division. For a cell to move from interphase to the mitotic phase, many internal and external conditions must be met. The three stages of interphase are called G1, S, and G2.

    G1 PHASE

    The first stage of interphase is called the G1 phase, or first gap, because little change is visible. However, during the G1 stage, the cell is quite active at the biochemical level. The cell is accumulating the building blocks of chromosomal DNA and the associated proteins, as well as accumulating enough energy reserves to complete the task of replicating each chromosome in the nucleus.

    S PHASE

    Throughout interphase, nuclear DNA remains in a semi-condensed chromatin configuration. In the S phase (synthesis phase), DNA replication results in the formation of two identical copies of each chromosome—sister chromatids—that are firmly attached at the centromere region. At this stage, each chromosome is made of two sister chromatids and is a duplicated chromosome. The centrosome is duplicated during the S phase. The two centrosomes will give rise to the mitotic spindle, the apparatus that orchestrates the movement of chromosomes during mitosis. The centrosome consists of a pair of rod-like centrioles at right angles to each other. Centrioles help organize cell division. Centrioles are not present in the centrosomes of many eukaryotic species, such as plants and most fungi.

    G2 PHASE

    In the G2 phase, or second gap, the cell replenishes its energy stores and synthesizes the proteins necessary for chromosome manipulation. Some cell organelles are duplicated, and the cytoskeleton is dismantled to provide resources for the mitotic spindle. There may be additional cell growth during G2. The final preparations for the mitotic phase must be completed before the cell is able to enter the first stage of mitosis.

    THE MITOTIC PHASE

    To make two daughter cells, the contents of the nucleus and the cytoplasm must be divided. The mitotic phase is a multistep process during which the duplicated chromosomes are aligned, separated, and moved to opposite poles of the cell, and then the cell is divided into two new identical daughter cells. The first portion of the mitotic phase, mitosis, is composed of five stages, which accomplish nuclear division. The second portion of the mitotic phase, called cytokinesis, is the physical separation of the cytoplasmic components into two daughter cells.

    MITOSIS

    Mitosis is divided into a series of phases—prophase, prometaphase, metaphase, anaphase, and telophase—that result in the division of the cell nucleus ([Figure 2]).

    Art Connection

    Figure 2: Animal cell mitosis is divided into five stages—prophase, prometaphase, metaphase, anaphase, and telophase—visualized here by light microscopy with fluorescence. Mitosis is usually accompanied by cytokinesis, shown here by a transmission electron microscope. (credit “diagrams”: modification of work by Mariana Ruiz Villareal; credit “mitosis micrographs”: modification of work by Roy van Heesbeen; credit “cytokinesis micrograph”: modification of work by the Wadsworth Center, NY State Department of Health; donated to the Wikimedia foundation; scale-bar data from Matt Russell)

    Which of the following is the correct order of events in mitosis?

    Sister chromatids line up at the metaphase plate. The kinetochore becomes attached to the mitotic spindle. The nucleus re-forms and the cell divides. The sister chromatids separate.

    Source : opentextbc.ca

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