The Cell Cycle and Mitosis

The cell cycle is a sequence of growth and division that cells go through.
It’s split into two main stages: interphase and mitosis.
During interphase, the cell grows, carries out normal cellular functions, and duplicates its DNA in preparation for division.
It is the longest phase of the cell cycle.

Interphase is subdivided into three stages: G1, S, and G2.
In the G1 phase, the cell grows and prepares for DNA replication. This phase is followed by a ‘checkpoint’ to verify everything is ready for DNA synthesis.
During the S phase, DNA replication occurs, resulting in two identical copies of each chromosome.
In the G2 phase, the cell continues to grow and prepare for division, which includes producing proteins necessary for mitosis and another checkpoint to check for any DNA damage.

Mitosis is the division of the nucleus into two genetically identical nuclei.
It consists of four stages: prophase, metaphase, anaphase, and telophase.
During prophase, chromosomes condense and become visible; the nuclear envelope breaks down.
Metaphase sees the chromosomes align in the middle of the cell, a formation known as the metaphase plate.
Anaphase is characterised by sister chromatids being pulled apart to opposite ends of the cell.
In telophase, a nuclear membrane forms around each set of chromosomes, and they begin to decondense, marking the end of mitosis.
The process of cytokinesis follows, dividing the cytoplasm to create two separate daughter cells.

The cell cycle is vital for growth, renewal and repair in multicellular organisms.
Cell division allows for an increase in the number of cells, contributes to the growth of tissues, and allows for repair of damaged cells.
Errors in the cell cycle can lead to uncontrolled cell growth and subsequently, cancer. This underlines the importance of the cell cycle checkpoints in maintaining regulation and preventing malignant cell proliferation.