A cell divides into two daughter cells.
The stages of the cell cycle, also called phases, are the components that make up the life cycle of a cell. There are four stages in a cell cycle, gap phase 1 (G1), synthesis (S), gap phase 2 (G2), and mitosis (M). Mitosis is divided into four stages, prophase, metaphase, anaphase, and telophase. Some descriptions of cell cycle stages include a third gap phase, known as G0.
The stages of mitosis.
The G1, S, and G2 stages are collectively known as interphase. A cell in the G1 phase is actively growing and undergoing the metabolic changes necessary for cell division. The G1 phase ends at the restriction point, when the cell “decides” to divide and enters S phase.
All DNA in the cell is replicated during the synthesis phase of the cell cycle stages. During DNA synthesis or replication, special cellular components separate the double-stranded DNA helix into two single strands. An enzyme called DNA polymerase runs along each template strand of DNA and builds on a second strand to exactly copy the cell’s original DNA. Other enzymes in the cell check that the DNA has been copied correctly. The end result of the synthesis is two exact double-stranded copies of the cell’s original DNA, called chromosomes.
Cells prepare for mitosis during the second gap stage. Special materials are needed in the cytoplasm of the cell for mitosis to occur. The cell undergoes metabolic changes during G2 to form these cytoplasmic materials.
In mitosis, a cell replicates its DNA before dividing into two daughter cells.
After G2, mitosis begins with the prophase stage. During this phase a structure known as the mitotic spindle is formed. Another structure called the centrosome duplicates, and the duplicates move to opposite ends of the cell. The chromosomes move toward a region of the mitotic spindle called the metaphase plate, and the centromeres are attached to the spindle by structures known as kinetochores. This last stage of prophase is sometimes divided into a stage called prometaphase.
During metaphase, the chromosomes line up with the metaphase plate to help the chromosomes separate properly during anaphase. Once the chromosomes are aligned, anaphase occurs when the chromosomes separate and move to opposite ends of the cell. The separate chromosomes are called daughter chromosomes.
Telophase is the final phase of mitosis and the steps of the cell cycle. Each of the daughter chromosomes acquires its own nuclear membranes, and the spindle fibers break off and disappear. However, cell division is not complete until cytokinesis occurs and the cell completely divides into two new cells. At this point, the cell cycle begins again with G1.
Some researchers include a fifth phase of the cell cycle stages. The G0 phase is inserted between mitosis and G1. If the cells enter the G0 phase, they no longer grow. However, they can reactivate and re-enter the G1 phase.