Mitosis is a biological process that allows a single cell to duplicate itself, serving as the mechanism behind growth and tissue repair in the body. The process always begins with one parent cell initiating the division. This cell duplication ensures the transfer of the parent cell’s entire set of genetic information into two new cells. The following steps detail how that initial cell prepares, divides, and ultimately becomes two separate, functional descendants.
The Starting Cell: Preparation for Division
The parent cell must first complete a preparatory stage called interphase. This stage, which occupies the majority of a cell’s life cycle, ensures the cell is ready to divide its contents evenly. During the synthesis (S) phase of interphase, the cell replicates its entire genome, creating an exact copy of every chromosome. This replication guarantees that there is enough genetic material to be distributed between the two future daughter cells.
Although the cell count remains one, the genetic content is effectively doubled, resulting in structures known as sister chromatids. These identical chromatids remain attached, forming the characteristic X-shape of a duplicated chromosome. Following the S phase, the cell enters the second gap (G2) phase, where it synthesizes proteins and duplicates organelles required for the physical division. This preparation phase ensures the single starting cell has all the necessary components to form two complete and identical cells.
The Mechanics of Mitosis: Splitting the Single Cell
Mitosis, known as the M phase, begins after the single parent cell is prepared with duplicated DNA and necessary proteins. The process starts with the chromosomes condensing and becoming visibly defined structures during prophase. Next, in metaphase, the duplicated chromosomes align precisely along the cell’s center plane, often referred to as the metaphase plate. This alignment is a checkpoint that verifies all chromosomes are correctly attached to the spindle fibers, which are structures made of microtubules.
The physical separation of the genetic material occurs in anaphase, where the sister chromatids are pulled apart by the shortening spindle fibers toward opposite poles of the cell. Once separated, each chromatid is considered a full, individual chromosome, and their movement defines the division of the nuclear contents, a process called karyokinesis. Finally, in telophase, a new nuclear envelope forms around each complete set of chromosomes at the poles of the cell, creating two distinct nuclei within the parent cell boundary. The final step, cytokinesis, involves the cytoplasm dividing, where the cell membrane pinches inward until the single cell splits entirely into two separate entities.
The Outcome: Two Identical Daughter Cells
Mitosis results in the formation of two daughter cells from the original parent cell. These two new cells are characterized by their exact genetic duplication, meaning they each contain an identical set of chromosomes. This precise duplication ensures that all somatic cells, which include most body cells like skin, liver, and muscle cells, maintain the same genetic blueprint.
The biological role of this duplication is the replacement of damaged or old cells and the overall increase in cell number required for organismal growth. Mitosis produces diploid cells, meaning they contain two sets of chromosomes, one inherited from each biological parent. This is in contrast to meiosis, a different division process that starts with one cell but produces four genetically unique cells that are haploid, specifically for sexual reproduction. The two daughter cells generated by mitosis can then enter interphase and begin the cycle again, allowing for continuous tissue maintenance and repair.