The Cell Cycle: Review of The Process and Main Features

The cell cycle is the meticulous series of events that parent cells go through as they grow and divide their cellular material between two new daughter cells. It is composed of four vital phases, G1, S Phase, G2, and M Phase, that ensure the process completes smoothly. G1, S Phase, and G2 collectively comprise Interphase, the longest step of the cycle, where the cell increases in size, replicates its DNA through duplication of chromosomes, and prepares for division in M Phase.

Following the completion of Interphase, the parent cell proceeds to M Phase, Mitotic Phase, the period consisting of Mitosis and Cytokinesis where the cell actually divides. Mitosis, division of the nucleus, can be further broken down into Prophase, Metaphase, Anaphase and Telophase.

Commencing Prophase, the preparation phase, the cell’s nuclear membrane disappears and duplicated chromosomes, two sister chromatids constructed of DNA and proteins, condense. In animal cells, centrioles, lying in the centrosome, separate to opposite poles. During this phase, spindles, microtubules that will separate the chromatids, begin to form.

Next, the cell becomes organized in Metaphase, where its chromosomes align in the center to form the Metaphase Plate. Also, spindle fibers attach to the chromosome’s centromere, the middle of a chromosome, where each pair of sister chromatids attach.

After Metaphase, the parent cell, now in the shape of an oval, begins to separate. The spindles shorten and pull the sister chromatids to opposite poles, splitting the chromosomes in half. The cell then moves on to Telophase where its inside divides and two new nuclear membranes form. The cell also begins to pinch in at the middle forming a cleavage furrow.

Finally, at the end of Mitosis, the parent cell undergoes cytokinesis, or division of the cytoplasm. This process varies for plant cells who form a cell plate, which divides the two nuclei and eventually becomes the cell wall. Both animal and plant cells, however, have the same end result: two daughter cells that repeat the cycle over again