3.3 Mitosis

During the S-phase of interphase the chromosomes replicate so that each chromosome has two sister chromatids attached at the centromere. After S-phase and G2, the cell enters Mitosis. The first step in mitosis is prophase, where the nucleus dissolves and the replicated chromosomes condense into the visible structures we associate with chromosomes. Next is metaphase, where the microtubules attach to the kinetochore and the chromosomes align along the middle of the dividing cell, known as the metaphase plate. The kinetochore is the region on the chromosome where the microtubules attach. It contains the centromere and proteins that help the microtubules bind. Then in anaphase, each of the sister chromatids from each chromosome gets pulled towards opposite poles of the dividing cell. Finally in telophase, identical sets of unreplicated chromosomes (single chromatids) are completely separated from each other into the two daughter cells, and the nucleus re-forms around each of the two sets of chromosomes. Following this is the partitioning of the cytoplasm (cytokinesis) to complete the process and to make two identical daughter cells. An acronym to remember the main stages of mitosis is iPMAT, where the little (lowercase) i stands for interphase.

A diagram with many details of mitosis, including notes on each stage and corresponding microscope images
Figure 3.3.1 Summarizing the Various Stages of Mitosis

Take as look at the following video, Cell Biology |Cell Cycle: Interphase & Mitosis, by Ninja Nerd (2018) on YouTube, which discusses the various stages of the Cell Cycle.

You should note that this is a dynamic and ongoing process, and cells don’t just jump from one stage to the next.

Microscope images of root cells in anaphase and prophase showing chromosomes stained purple
Figure 3.3.2 Root Meristem of Vicia Faba (Cells in Anaphase, Prophase)

Keep in mind the following points that outline the importance and significance of mitosis:

  • Keeps chromosome number constant
  • Maintains genetic stability in daughter cells
  • Helps in growth and development of the zygote
  • Helps in repair and regeneration
  • Restores nucleo-plasmic ratio
  • Checks cell size and maintains a favourable surface area/volume ratio.

 How Mitosis Helps to Maintain Genetic Stability

Mitosis results in the splitting of replicated chromosomes during cell division and facilitates the generation of two new identical daughter cells. Given that chromosomes form from parent chromosomes by making exact copies of their DNA, mitosis helps in preserving and maintaining the genetic stability of a particular population.

Watch the video, Animation How the Cell Cycle Works, by Marcin Gorzycki (2018) on YouTube, which discusses the various stages of Mitosis. 

Media Attributions

References

Betts et al. (2016, October 21). Figure 3.32 Cell division: Mitosis followed by cytokinesis [digital image]. Anatomy and Physiology. OpenStax. https://openstax.org/books/anatomy-and-physiology/pages/3-5-cell-growth-and-division

Marcin Gorzycki. (2013, March 14). Animation how the cell works (video file). YouTube. https://youtu.be/g7iAVCLZWuM”>https://youtu.be/g7iAVCLZWuM”>https://youtu.be/g7iAVCLZWuM

Ninja Nerd. (2018, January 7). Cell biology | Cell cycle: Interphase & mitosis (video file). YouTube. https://youtu.be/LUDws4JrIiI”&gt

Reischig, J. (2014). Mitosis: pressure; root meristem; Vicia faba, A, P, 1500x  [digital micrographic image]. Mantis. https://www.mantis.cz/mikrofotografie/pages/261_10.html

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Open Genetics by Natasha Ramroop Singh, Thompson Rivers University is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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