for . A cell typically spends most of its life in this phase. This phase is sometimes referred to as Gap 1. Synthesis Phase (S): during this phase, the cell’s DNA is copied in the process of DNA replication. Growth Phase 2 (G2): during this phase, the cell makes final preparations to divide. For example, it makes additional and . This phase is sometimes referred to as Gap 2. Control of the Cell Cycle If the cell cycle occurred without regulation, might go from one phase to the next before they were ready. What controls the cell cycle? How does the cell know when to grow, synthesize DNA, and divide? The cell cycle is controlled mainly by regulatory . These proteins control the cycle by signaling the cell to either start or delay the next phase of the cycle. They ensure that the cell completes the previous phase before moving on. Regulatory proteins control the cell cycle at key checkpoints, which are shown in Figure . There are a number of main checkpoints. The G1 checkpoint, just before into S phase, makes the key decision of whether the cell should divide. The S checkpoint determines if the DNA has been replicated properly. The mitotic spindle checkpoint occurs at the point in metaphase where all the should have aligned at the mitotic plate. Checkpoints in the eukaryotic cell cycle ensure that the cell is ready to proceed before it moves on to the next phase of the cycle. Cancer is a disease that occurs when the cell cycle is no longer regulated. This may happen because a cell’s DNA becomes damaged. Damage can occur due to exposure to hazards such as radiation or toxic chemicals. Cancerous generally divide much faster than normal cells. They may form a mass of abnormal cells called a tumor (see Figure ). The rapidly dividing cells take up nutrients and space that normal cells need. This can damage tissues and organs and eventually lead to death.
for . A cell typically spends most of its life in this phase. This phase is sometimes referred to as Gap 1. Synthesis Phase (S): during this phase, the cell’s DNA is copied in the process of DNA replication. Growth Phase 2 (G2): during this phase, the cell makes final preparations to divide. For example, it makes additional and . This phase is sometimes referred to as Gap 2. Control of the Cell Cycle If the cell cycle occurred without regulation, might go from one phase to the next before they were ready. What controls the cell cycle? How does the cell know when to grow, synthesize DNA, and divide? The cell cycle is controlled mainly by regulatory . These proteins control the cycle by signaling the cell to either start or delay the next phase of the cycle. They ensure that the cell completes the previous phase before moving on. Regulatory proteins control the cell cycle at key checkpoints, which are shown in Figure . There are a number of main checkpoints. The G1 checkpoint, just before into S phase, makes the key decision of whether the cell should divide. The S checkpoint determines if the DNA has been replicated properly. The mitotic spindle checkpoint occurs at the point in metaphase where all the should have aligned at the mitotic plate. Checkpoints in the eukaryotic cell cycle ensure that the cell is ready to proceed before it moves on to the next phase of the cycle. Cancer is a disease that occurs when the cell cycle is no longer regulated. This may happen because a cell’s DNA becomes damaged. Damage can occur due to exposure to hazards such as radiation or toxic chemicals. Cancerous generally divide much faster than normal cells. They may form a mass of abnormal cells called a tumor (see Figure ). The rapidly dividing cells take up nutrients and space that normal cells need. This can damage tissues and organs and eventually lead to death.