Mitosis is a biological process where a single cell divides into two genetically identical daughter cells. This cell division serves several essential purposes in living organisms, facilitating growth in multicellular organisms and replacing worn-out or damaged cells for tissue repair and maintenance. For single-celled organisms, it is a method of asexual reproduction. Errors in this multi-step process can lead to cellular abnormalities.
Prophase
Prophase is the initial stage of mitosis, with significant changes occurring in the cell’s nucleus and cytoplasm. The loosely organized genetic material, chromatin, condenses into compact, visible chromosomes. Each condensed chromosome consists of two identical copies, called sister chromatids, joined at the centromere.
As chromosomes condense, other cellular components reorganize. The nucleolus disappears, and the nuclear envelope begins to break down. In the cytoplasm, the mitotic spindle begins to form from microtubules extending from centrosomes. These centrosomes move towards opposite poles of the cell, establishing the framework for chromosome separation.
Metaphase
The cell enters metaphase, characterized by the precise alignment of chromosomes. The mitotic spindle fibers fully develop and extend across the cell. These spindle fibers attach to the centromeres of each chromosome at specialized protein structures called kinetochores.
Chromosomes congregate along the cell’s equatorial plane, forming the metaphase plate. This central alignment ensures each new daughter cell receives an exact and complete set of genetic information. This balanced alignment is maintained by opposing pulling forces from microtubules at each pole.
Anaphase
Anaphase is a stage of mitosis where duplicated chromosomes are separated. The centromeres holding sister chromatids together split. Once separated, each sister chromatid is considered an individual chromosome.
Spindle fibers attached to these chromosomes shorten, pulling them towards opposite poles of the cell. The cell often elongates, preparing for division. By the end of anaphase, an identical set of chromosomes has arrived at each pole, ensuring genetic material is evenly distributed.
Telophase
Telophase is the final stage of nuclear division in mitosis. As chromosomes arrive at opposite poles, they decondense, returning to a less compact, diffuse state. This decondensation allows the genetic material to become functional within the newly forming nuclei.
New nuclear envelopes begin to form around each set of chromosomes at the cell poles, creating two distinct nuclei. The mitotic spindle fibers also disassemble. While telophase concludes nuclear division, cytokinesis, the division of the cell’s cytoplasm, typically overlaps and follows, resulting in two separate, genetically identical daughter cells.