Mitosis: Phases, Regulation, and Clinical Significance

Mitosis is the process of nuclear division in eukaryotic cells that produces two genetically identical daughter cells. It is central to growth, tissue repair and asexual reproduction, and it is tightly regulated to preserve genomic integrity. Mitosis is conventionally divided into four main phases. During prophase, chromatin condenses into visible chromosomes and the nuclear envelope breaks down. In metaphase, chromosomes line up along the cell equator, attached to spindle fibres at their centromeres. In anaphase, sister chromatids are pulled apart toward opposite poles of the cell. In telophase, nuclear envelopes re-form around each set of chromosomes and the chromosomes decondense. Cytokinesis then divides the cytoplasm, producing two daughter cells. The process is essential for growth, tissue repair and asexual reproduction. Because each daughter cell must receive an exact copy of the genome, errors in mitosis can lead to aneuploidy (an abnormal number of chromosomes) and are associated with cancer. To prevent such errors, the cell cycle contains checkpoints controlled by cyclins and cyclin-dependent kinases (CDKs). These regulatory proteins ensure that DNA is replicated correctly before division proceeds, coupling the completion of one stage to the initiation of the next. In summary, mitosis is a four-phase process of chromosome segregation followed by cytokinesis, supported by a checkpoint control system that safeguards the accuracy of DNA replication and chromosome distribution.