mítósis

Mitosis, or mitóza, is a division process in eukaryotic cells that distributes a parent cell's genetic material into two genetically identical daughter nuclei. It is part of the broader cell cycle and is typically followed by cytokinesis, which splits the cytoplasm to form two separate cells.

During prophase, chromatin condenses into visible chromosomes and the mitotic spindle forms outside the nucleus. The nucleolus disappears and the nuclear envelope begins to break down. In prometaphase, microtubules attach to kinetochores at the centromeres, and chromosomes begin moving toward the center of the cell. In metaphase, chromosomes align along the equatorial plane, held in place by microtubules attached to kinetochores from opposite poles. In anaphase, sister chromatids detach and are pulled to opposite poles as kinetochore microtubules shorten; non-kinetochore microtubules lengthen to push poles farther apart. In telophase, the chromosomes arrive at poles and de-condense; the nuclear envelope re-forms, and the nucleolus reappears.

Cytokinesis completes cell division by dividing the cytoplasm. In animal cells, a contractile actin ring forms a cleavage furrow that splits the cell membrane to yield two daughter cells. In plant cells, vesicles coalesce at the center to form a cell plate that develops into separating cell walls.

Regulation of mitosis is tightly controlled by the cell cycle, with checkpoints such as the G2/M and spindle assembly checkpoints ensuring DNA is replicated and chromosomes are correctly attached before segregation. Cyclins and cyclin-dependent kinases coordinate progression. Errors in mitosis can lead to aneuploidy and genomic instability.

Mitotic division preserves the chromosome number and produces identical somatic cells, in contrast to meiosis, which reduces chromosome number and increases genetic diversity.