5.1 The Cell Cycle PDF

5.1 The Cell Cycle KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions. MAIN IDEAS VOCABULARY...

5.1 The Cell Cycle KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions. MAIN IDEAS VOCABULARY The cell cycle has four main stages. cell cycle, p. 134 Cells divide at different rates. mitosis, p. 135 Cell size is limited. cytokinesis, p. 135 Connect Many of life’s little chores such as sweeping and dusting, are quietly satisfying and rather fun. Washing dishes by hand, however, is never fun, which is why some clever person made the dishwasher. This handy invention soaks, washes, and rinses your dishes to a spot-free, sanitary sparkle. You unload the dishes, and the machine is ready to start the cycle all over again. A cell goes through a cycle, too. This cycle of growth, DNA synthesis, and division is essen- tial for an organism to grow and heal. If it goes out of control, abnormal cell growth may occur, resulting in cancer cells like those shown on the previous page. MAIN IDEA The cell cycle has four main stages. Just as all species have life cycles, from tiny chihuahuas to massive beluga whales, cells also have a life cycle. The cell cycle is the regular pattern of growth, DNA duplication, and cell division that occurs in eukaryotic cells. FIGURE 5.1 Cells grow and copy FIGURE 5.1 shows its four main stages: gap 1, synthesis, gap 2, and mitosis. Gap their DNA during interphase. 1, synthesis, and gap 2 together make up what is called interphase. They also carry out cell-specific functions in G1 and G2. During The stages of the cell cycle get their names from early studies of cell M stage, both the nucleus division. Scientists’ observations were limited by the microscopes of the time. (in mitosis) and cytoplasm When a cell was not actively dividing, they could not see (in cytokinesis) are divided. >CI:GE=6H: activity in it. Thus, they originally divided the cell cycle into two parts: interphase, when the cell appeared to be at rest, and mitosis, when the cell was dividing. Improved techniques and tools later allowed H IZade]Vh Z Since they still could not see anything B^idh^hB 6cVe]VhZ 8ZaaY^k^h^dc happening during the other parts of inter- ]Vh Z phase, scientists named the periods between B ZiVe H>H ] VhZ mitosis and synthesis “gap 1” and “gap 2.” B>ID Egde Hnci]Zh^hH Eventually, scientists learned that, during