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Biomedical Research

Mitosis and the Cell Cycle

The cell cycle is a process most cells go through that ultimately results in a cell dividing into two daughter cells. Although it may sound like a relatively simple process, every step of the process is very complex.

By Saharsh Satheesh

Published 5:40 PM EST, Mon February 8, 2021

Introduction

The cell cycle is a process most cells go through that ultimately results in a cell dividing into two daughter cells. Although it may sound like a relatively simple process, every step of the process is very complex.

The cell cycle is divided into two main sections: interphase and mitosis. Interphase is when a cell grows and replicates its DNA, while mitosis is when a cell splits into two identical copies of itself. So why do cells need to split into two? One reason is because if our cells are damaged, mitosis helps us create new cells to take the place of damaged or lost cells.

The cell spends the majority of its time in interphase, preparing to undergo mitosis. Furthermore, mitosis is the shortest phase of the cell cycle.  

Interphase

Interphase is made up of 3 separate phases: G1, S, and G2. During G1, the cell grows and acquires essentials for the upcoming DNA replication and mitosis. In the S phase, the DNA of the cell undergoes replication and the organelles and centrosomes start to duplicate. Organelles are membrane-bound structures in a cell. Centrosomes are organelles that produce spindle fibers during cell division. DNA replication is a complex process, but to put it in simple terms, the DNA replicates so that the two cells produced from mitosis have the same DNA. Finally, in the G2 phase, there is more growth, and the duplication of the organelles and centrosome complete. Upon completing these 3 sections of interphase, the cell may now undergo mitosis. 

Mitosis

Mitosis is made up of 5 distinguished sections: Prophase, prometaphase, metaphase, anaphase, and telophase, though some coin prometaphase and metaphase as simply metaphase. In prophase, the nucleus of the cell dissolves, and the DNA takes shape from chromatin, which is unraveled DNA, to chromosomes, which is tightly packed DNA. In addition, the centrosomes begin to move apart. In prometaphase, the nuclear lamina dissolves and spindle fibers begin to form. Kinetochores, which are protein structures that the spindle fibers attach to, form in the chromosomes. In metaphase, the spindle fibers complete attaching to the kinetochores, and as a result, the centrosomes get pushed even further to opposite ends of the cell, causing the chromosomes to line up in the middle. In anaphase, the tugging force from the centrosomes drifting apart pushes the chromosomes apart and they split down the middle. In telophase, the centrosomes get pushed apart so much that there are essentially two cells that are attached together by the middle. The nuclear lamina and nucleus reform, and chromosomes change back into chromatin. Finally, in cytokinesis, the cleavage furrow is split by the contractile ring which is made of actin filaments. The cell is pinched into two. At last, the cell has divided, and now the whole process may repeat.

Saharsh Satheesh, Youth Medical Journal 2021

References

“Cell Cycle.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., http://www.britannica.com/science/cell-cycle.

“Cell Cycle.” Genome.gov, http://www.genome.gov/genetics-glossary/Cell-Cycle.

“How Cells Divide.” PBS, Public Broadcasting Service, http://www.pbs.org/wgbh/nova/body/how-cells-divide.html.

“Https://Www.ncbi.nlm.nih.gov/Books/NBK9876/.” The Cell Cycle & Mitosis Tutorial, http://www.biology.arizona.edu/cell_bio/tutorials/cell_cycle/cells3.html.

“Phases of Mitosis | Mitosis | Biology (Article).” Khan Academy, Khan Academy, http://www.khanacademy.org/science/ap-biology/cell-communication-and-cell-cycle/cell-cycle/a/phases-of-mitosis.

Urry, Lisa A., et al. Campbell Biology, 11th Ed. Pearson, 2017.

By Saharsh Satheesh

Saharsh Satheesh is a junior in high school. He has a passion for biology and plans to study medicine in college.

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