Phases of Mitosis in Order: A Detailed Overview

Cell division is fundamental to life, enabling organisms to grow, repair tissues, and reproduce. Mitosis, a type of cell division, ensures that each daughter cell receives an identical set of chromosomes as the parent cell. This precise process is crucial for maintaining genetic stability across generations.

Understanding mitosis involves examining its distinct phases, each characterized by specific events and structures. Let’s delve into these stages to appreciate how cells orchestrate their division.

Prophase

Prophase marks the commencement of mitosis, setting the stage for chromosome segregation. During this phase, chromatin fibers condense into visible chromosomes, each composed of two sister chromatids joined at the centromere. The nucleolus becomes less distinct, and the nuclear envelope starts to disintegrate, allowing chromosomes to interact with cytoplasmic components. Centrosomes, having duplicated during interphase, migrate to opposite poles of the cell, organizing the mitotic spindle. This spindle, composed of microtubules, will later facilitate chromosome movement.

Prometaphase

Prometaphase involves several changes to facilitate precise chromosome segregation. The nuclear envelope disintegrates, allowing spindle microtubules to access chromosomes. Chromosomes, consisting of sister chromatids, move freely, enabling microtubules to attach to kinetochores at the centromere. This attachment, regulated by motor proteins, is crucial for accurate chromosome maneuvering. The spindle assembly checkpoint ensures all chromosomes are correctly attached before proceeding, preventing aneuploidy.

Metaphase

Metaphase ensures all systems are aligned for genetic material distribution. Chromosomes align at the metaphase plate, equidistant from spindle poles. Spindle fibers exert tension on kinetochores, ensuring each sister chromatid is poised for division. The spindle checkpoint monitors attachment and tension, safeguarding chromosome segregation. Motor proteins, like dynein and kinesin, maintain chromosome alignment until the transition to anaphase.

Anaphase

Anaphase marks the separation of sister chromatids, triggered by separase cleaving cohesin proteins. Freed chromatids, now individual chromosomes, are pulled toward opposite poles by shortening kinetochore microtubules. Spindle poles move apart, elongating the cell in preparation for division. Non-kinetochore microtubules, powered by motor proteins, ensure each daughter cell receives an exact genetic copy.

Telophase

In telophase, nuclear integrity is reestablished, preparing for final separation. Chromosomes de-condense, and the nuclear envelope reforms around each set of chromosomes. Nucleoli reappear, signaling the resumption of ribosomal RNA synthesis. The reassembly of the nuclear envelope protects genetic material and sets the stage for cellular differentiation in daughter cells.

Cytokinesis

Cytokinesis focuses on the physical separation of the cytoplasm, forming two distinct daughter cells. A contractile ring of actin and myosin filaments assembles beneath the plasma membrane, creating a cleavage furrow that pinches the cell into two. In plant cells, a cell plate forms, developing into a new cell wall. Cytokinesis ensures each daughter cell receives equal genetic material and sufficient organelles, completing the cell cycle.