The cell spends the majority of its life cycle in interphase. During interphase, the cell is growing and replicating DNA. Interphase is composed of three phases: the Gap 1 phase, synthesis and the Gap 2 phase. During Gap 1, the cell is growing and performing normal cell functions. During synthesis, the cell replicates all of its DNA. Gap 2 phase is like a checkpoint for the cell, ensuring that it is healthy enough to proceed with mitosis.
Mitosis is the process of cell division, which is how new cells are created in living organisms. Mitosis has four stages: prophase, metaphase, anaphase and telophase. During prophase, chromosomes become visible and centrioles move to opposite sides of the cell. In metaphase, chromosomes line up in the center of the cell. During metaphase, the chromosomes split into two chromatids, each of which moves toward opposite sides of the cell. In telophase, a nuclear membrane starts forming around each set of chromatids and cytokinesis begins.
Cytokinesis is the final phase in cell division. Cytokinesis is the process by which a single cell divides its cytoplasm between its two daughter cells. Animal cells and plant cells differ in how cytokinesis happens. In animal cells, the cells are divided in two by a pinching of the cytoplasm. However, plant cells have rigid cell walls, so the cell builds a new cell wall, forming two separate cells. When cytokinesis is complete, two identical cells have formed from a single cell.
During interphase, cells sometimes enter a phase known as the Gap 0, or G0, phase. During G0, cells do not grow or divide. Cells might enter into the G0 phase because of a lack of nutrients or because certain cells, such as neurons, reach maturity. Cells in the G0 phase are known as post-mitotic cells. Under certain circumstances, post-mitotic cells can be induced to re-enter the Gap 1 phase and restart mitosis.