The cell cycle is the process by which a cell duplicates its DNA and divides to produce two daughter cells. It is a series of events that include interphase and mitosis. Interphase is made up of three subsets and is where the cell duplicates its DNA and grows in preparation for mitosis. Mitosis is the process in which cell division occurs. Phosphorylated cyclin and cyclin-dependent kinase complexes are used to promote the cell cycle. They regulate the cell cycle and phosphorylate other proteins that further promote the cycle. Say no to plagiarism. Get a tailor-made essay on "Why Violent Video Games Shouldn't Be Banned"? Get an Original Essay The first interphase is gap phase one (G1 phase). During this phase the cell grows and prepares for DNA synthesis. Mitochondrial respiration provides energy for growth. After the G1 phase the cell passes the first checkpoint, the restriction point. At this checkpoint, if there is DNA damage or other external factors, you do not move on to the next step. Negative regulatory molecules (retinoblastoma protein, p53 and p21) are responsible for preventing the cell from moving to the next phase until the damaged DNA is repaired. The second interphase is the synthesis phase (G2 phase). This is where DNA duplication occurs and all chromosomes are replicated. DNA polymerase is used to synthesize DNA molecules that are essential for replication. After synthesis, the cell passes through the S checkpoint. This checkpoint ensures that all the chromosomes and DNA that have been replicated are not damaged, so the cell can move into the third interphase. The final interphase is gap phase two (G2 phase). During this phase the cell undergoes further growth and prepares for mitosis. Biosynthesis occurs which involves the production of microtubules, necessary for the mitosis phase. After passing through the final interphase, the cell passes through the G2 checkpoint. This step verifies that the replicated DNA is not damaged and that all chromosomes have been replicated. The cell is then suited to go through the mitosis stage. The mitosis stage is composed of three subphases, the prophase stage, the metaphase stage, the anaphase stage and the telophase stage. During prophase, mediated by the condensation complex, chromatin condenses into the structure of chromosomes. This process is called chromatin condensation. The condensed, coiled chromosomes then move into metaphase, where they align in the center of the cell and then separate into two daughter cells. The cell then passes through the M checkpoint, at this point it is determined whether the sister chromatids are correctly attached to the spindle microtubules, if they are correctly attached the cell can then enter anaphase. In anaphase all chromatids separate and align with the spindle fibers. Then in telophase the cell membrane is formed, the nucleoli and all the other organelles appear. The two daughter cells are fully formed. The cycle repeats itself continuously. Please note: this is just an example. Get a custom paper from our expert writers now. Get a Custom Essay There is an additional phase in the cell cycle called the G0 phase. This is known as the resting phase and some cells rest in this phase which can be quiescence if they receive a division or senescence signal. The cells in this phase are alive and carry out their functions but do not prepare for division, divide slowly or not at all.