You were once composed of a single cell: the zygote. Today, you are a multicellular organism composed of about 37 trillion cells. Each of your organs is made up of specialized cells working together with the rest of the organs to support your whole body. How exactly did you go from being composed of a single cell to being composed of trillions of cells? The answer is cell division.
What is cell division?
Cell division is an important part of the cell cycle or the cell life. Through the process of cell division, a cell splits into two cells. This process helps us grow as well as repair and even reproduce. There are two types of cell divisions: mitosis and meiosis. Mitosis occurs for somatic or body cells, via which identical copies of the parent cell are created. Meiosis, however, is for gametes specifically or the reproductive cells—the sperm and the egg. The process of meiosis produces four daughter cells that are not identical to the parent but rather different. We will specifically be discussing eukaryotic mitotic cell division in this article.
What you need to know about the Cell Cycle
The cell cycle represents the general life of a cell, and it has been separated into two main stages: interphase and the mitotic phase. Interphase refers to the part of the cell's life when it hasn't started dividing yet. This stage has three phases: G1, S phase (or the synthesis phase), and G2.The second stage is the mitotic cycle, where the process of division has started. It consists of two main sections: mitosis and cytokinesis. Mitosis is the division of genetic material and consists of phases—prophase, prometaphase, metaphase, anaphase, and telophase. Finally, there is cytokinesis, which refers to the division of the cell's cytoplasm.
Closer look at Interphase
The Interphase takes up 90% of the cell cycle. In phase G1, also referred to as the first gap, the cell is active and carrying out its duties while also growing. In the S phase, the cell is replicating DNA to prepare for the eventual division in the mitotic stage. Replication of DNA is extremely important for cell division, as the body needs to ensure that each of the new cells has an equal amount of genome; otherwise, health issues and mutations can arise. Thus, in this S phase, the cell doubles its DNA so that it can be evenly divided into the two daughter cells. Finally, the G2 phase, similar to the G1 phase, consists of the cell being metabolically active, fulfilling its duties, and also growing. Although, since this step is right before the mitotic stage starts, the second gap or G2 serves as a preparatory step for the division, and certain proteins necessary for division are created here.
The Mitotic stage
As we previously discussed, the mitotic stage consists of two main sections: mitosis, which refers to the division of the genetic material, and cytokinesis, which is the division of cytoplasm. Mitosis itself is made up of five stages.
Prophase is the first one; here, the DNA condenses in length and size to become more compacted so that the division process is easier to perform. As this step occurs after the S phase, where the DNA was replicated, the DNA is present in the form of sister chromatids, which come together to form one chromosome attached at the middle point called the centromere, where they also have specialized proteins called kinetochores.
Prometaphase is a preparatory step for the metaphase, which is the next phase. Here, the spindle fibers made of microtubules have attached to the kinetochores of chromosomes. These spindles are coming out from centrosomes, which reside at each end pole of the cell.
Metaphase is when the spindle fibers on both ends of the cell are pulling on the chromosomes to the point that the pulling results in a sort of draw, creating an imaginary plate in the middle where approximately all the chromosomes are lined up.
Anaphase is when the sister chromatids are separated, creating two chromosomes and pulling them away from each other. The kinetochore proteins allow for even splitting of the chromosomes, which is essential for the daughter cells to be exactly identical.
Finally, telophase is when the DNA is pulled to each end of the elongated cell, and two nuclei, one for each new cell, have begun to appear. The spindles have dissolved at this point, and a cleavage furrow is beginning to form.
Cytokinesis, the last phase before the division occurs simultaneously with telophase and pinches off the cells at the developing cleavage furrow, separating the cytoplasm and successfully creating two daughter cells.
Why is Cell division so important?
Cell division is essential as it enables us to grow and develop further. Additionally, it plays a crucial role in the repair process. If cells in one region are damaged, other cells can contribute by dividing and repairing the affected area. Cell division is an essential part of s as biological beings and will continue to occur for each and every moment we exist.
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