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7.3 Mitosis and Cytokinesis

The mitotic phase is the part of the eukaryotic cell cycle when the cell is dividing. It is a multistep process during which the duplicated chromosomes are aligned, separated, and moved to opposite poles of the cell. Then, the cell is divided into two new identical daughter cells. The mitotic phase consists of two overlapping processes: mitosis and cytokinesis.

Mitosis cycle of a eukaryote cell.
Figure 7.3.1 Mitosis is the phase of the eukaryotic cell cycle that occurs between DNA replication and the formation of two daughter cells. Image by LadyofHats, CC BY-NC 3.0
Figure 7.3.1 Description

The image is a diagram illustrating the process of mitosis, the type of cell division that results in two genetically identical diploid daughter cells.

  1. Starting Cell (Interphase): The diagram begins with a single diploid cell containing a nucleus with uncondensed chromatin.DNA Replication occurs, and chromosomes duplicate, each consisting of two sister chromatids.
  2. Chromosomes Align (Metaphase): The chromosomes, now condensed and visible, align at the center of the cell on the metaphase plate. The spindle fibres are attached to the centromeres of the chromosomes.
  3. Sister Chromatids Separate (Anaphase-Telophase): The sister chromatids are pulled apart by spindle fibres and move towards opposite poles of the cell. The cell starts to elongate, and the nuclear envelope begins to reform.
  4. Formation of Two Diploid Cells (Cytokinesis): The cell membrane pinches in, leading to the formation of two genetically identical diploid daughter cells. Each daughter cell has the same chromosome number as the original parent cell.

Mitosis

Mitosis is the process in which the nucleus of a eukaryotic cell divides. During mitosis, the two sister chromatids that make up each chromosome separate from each other and move to opposite poles of the cell. This type of cell division begins with one diploid cell and results in two identical diploid daughter cells. Mitosis is used for growth and replacing dead or damaged cells. It can also be used for asexual reproduction in some organisms.

Mitosis occurs in four phases: prophase, metaphase, anaphase, and telophase. Expand each phase below to learn more.

 

Phase 1: Prophase
Phase 2: Metaphase
Phase 3: Anaphase
Phase 4: Telophase

Cytokinesis

Cytokinesis is the second part of the mitotic phase, during which cell division is completed by the physical separation of the cytoplasmic components into two daughter cells. Although the stages of mitosis are similar for most eukaryotes, the process of cytokinesis is quite different for eukaryotes with cell walls, such as plant cells.

In cells such as animal cells that lack cell walls, cytokinesis begins following the onset of anaphase. A contractile ring composed of actin filaments forms inside the plasma membrane at the former metaphase plate. The actin filaments pull the cell’s equator inward, forming an indentation called the cleavage furrow. The furrow deepens as the actin ring contracts, and eventually, the membrane and cell are split in two (Figure 7.3.6).

A cleavage furrow is impossible in plant cells because of the rigid cell walls surrounding the plasma membrane. A new cell wall must form between the daughter cells. During interphase, the Golgi apparatus accumulates enzymes, structural proteins, and glucose molecules prior to breaking up into vesicles and dispersing throughout the dividing cell. These Golgi vesicles move on microtubules to collect at the metaphase plate during telophase. There, the vesicles fuse from the centre toward the cell walls; this structure is called a cell plate. As more vesicles fuse, the cell plate enlarges until it merges with the cell wall at the cell’s periphery. Enzymes use the glucose that has accumulated between the membrane layers to build a new cell wall of cellulose. The Golgi membranes become the plasma membrane on either side of the new cell wall (Figure 7.3.6).

 

Comparison of cytokinesis in an animal and plant cell.
Figure 7.3.6 (a) A cleavage furrow divides animals cell.  (b) A cell plate divides plant cells Image by OpenStax, CC BY 4.0

Exercise 7.3.1

Text Description

Drag to arrange the images in the correct sequence

  1. An image illustrating telophase and cytokinesis
  2. An image illustrating anaphase
  3. An image illustrating metaphase
  4. An image illustrating prophase

Answers:

    1. An image illustrating prophase
    2. An image illustrating metaphase
    3. An image illustrating anaphase
    4. An image illustrating telophase and cytokinesis
Text Description
1. Fibres called centrioles attach to the centromeres during mitosis. (True/False)
2. Chromosomes begin to uncoil during anaphase. (True/False)
3. During metaphase, sister chromatids line up along the equator of the cell. (True/False)
4. After mitosis, the result is typically two daughter cells with identical DNA to each other. (True/False)

Answers:
1. False
2. False
3. True
4. True

4.13 Mitosis and Cytokinesis” from Human Biology by Christine Miller is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License, except where otherwise noted.

6.2 The Cell Cycle” from Biology and the Citizen by Colleen Jones is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

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Biology Essentials 1 Copyright © 2025 by Kari Moreland is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.