The continuity of life is fundamentally dependent on the process of cell division, a remarkable mechanism by which a single parent cell divides to form two or more daughter cells. This process is essential for the growth and development of multicellular organisms, the repair of tissues, and for reproduction. The sequence of events by which a cell duplicates its genome, synthesizes its other constituents, and eventually divides into two daughter cells is known as the cell cycle. A typical eukaryotic cell cycle is a highly regulated and ordered process, divided into two main phases: Interphase and the M Phase (Mitosis Phase).

Interphase is the preparatory and longest phase of the cell cycle, during which the cell grows and replicates its DNA in an orderly manner. It is further subdivided into three distinct stages: the G1 phase (Gap 1), the S phase (Synthesis), and the G2 phase (Gap 2). In the G1 phase, the cell is metabolically active and grows continuously, synthesizing proteins and RNA. This is followed by the S phase, a critical stage where DNA replication occurs, resulting in the duplication of the cell’s genetic material. Each chromosome, which initially consisted of a single chromatid, now consists of two identical sister chromatids joined at a centromere. Following the S phase, the cell enters the G2 phase, where it continues to grow and synthesize proteins required for the subsequent division.

The M Phase, or Mitosis Phase, represents the actual period of cell division. It is a dramatic and complex process that involves the precise segregation of duplicated chromosomes into two new nuclei, a process called karyokinesis, which is typically followed by the division of the cytoplasm, known as cytokinesis. The M phase itself is divided into four sequential stages: Prophase, Metaphase, Anaphase, and Telophase.

Mitosis, or equational division, is the process by which a parent cell divides to produce two genetically identical daughter cells, each containing the same number of chromosomes as the parent.

• • Prophase: This is the first stage, where the chromatin fibers condense and become visible as distinct chromosomes. The nuclear envelope begins to disintegrate, and the mitotic spindle starts to form.
  • Metaphase: The nuclear envelope completely disappears, and the condensed chromosomes align themselves at the equatorial plane of the cell, known as the metaphase plate.
  • Anaphase: The sister chromatids separate from each other at the centromere and are pulled towards opposite poles of the cell by the shortening spindle fibers.
  • Telophase: The chromosomes arrive at the opposite poles and decondense. A new nuclear envelope forms around each set of chromosomes, resulting in two distinct daughter nuclei.

Cytokinesis usually begins during late anaphase or telophase. In animal cells, this occurs through the formation of a cleavage furrow. In plant cells, a cell plate forms to create a new cell wall.

In contrast to mitosis, Meiosis is a specialized type of cell division that occurs in sexually reproducing organisms to produce gametes (sperm and eggs). It is a reductional division, meaning it reduces the chromosome number by half, from diploid (2n) to haploid (n). This is essential for maintaining a constant chromosome number across generations. Meiosis involves two sequential cycles of nuclear and cell division, Meiosis I and Meiosis II, but only a single cycle of DNA replication.

Meiosis I is the reductional division. A key event in its prophase I is synapsis, where homologous chromosomes pair up, and crossing over, where genetic material is exchanged between them. This process is a major source of genetic variation. In anaphase I, the homologous chromosomes separate and move to opposite poles, while the sister chromatids remain attached. This results in two haploid cells.

Meiosis II is an equational division, very similar to mitosis. In this phase, the sister chromatids of the chromosomes in the two haploid cells from Meiosis I are separated. The stages—Prophase II, Metaphase II, Anaphase II, and Telophase II—proceed much like their mitotic counterparts, ultimately resulting in the formation of four genetically distinct haploid daughter cells from the original diploid parent cell. This ensures genetic diversity in the offspring.