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Transcript
5.1 Cell Cycle Chapter 5 Cell Growth and Division and Growth Mr. Shilala DAHS KEY CONCEPT Cells have distinct phases of growth, reproduction, and normal functions. The cell cycle has four main stages: gap 1, synthesis, gap 2, and mitosis.. • The cell cycle is a regular pattern of growth, DNA replication, and cell division. • Stages get their name from early observations – Interphase when a cell was not dividing • Improvements in technology led interphase being called – Gap 1,DNA synthesis and Gap 2 • Realized during interphase cells carry out normal functions and grow – Mitosis when a cell was dividing Stages of Cell Cycle 1. Gap 1 (G1): – Cell growth and normal functions – Cell Spends majority of time here – Varies by type of cell – Must pass a critical checkpoint before going to synthesis stage • Like passing a physical before participating in sports 2. DNA Synthesis (S) – Cell copies DNA – Cell now contains 2 identical copies of DNA 3. Gap 2 (G2): – Additional growth – Cell is getting ready to divide – Also contains critical checkpoint • Undamaged DNA etc 4. Mitosis – division of cell nucleus – Two processes • Mitosis • Cytokinesis – cytoplasm splitting – Occurs only if the cell is large enough and the DNA undamaged Cells divide at different rates. • The rate of cell division varies widely with the need for those types of cells. G0 Stage • Stage when a cell reaches a point where it is highly unlikely to divide – Example: Neuron in spinal cord – Lymphocytes – divide only when invader enters body Cell size is limited and determined by the SA to V ratio. • Cells have upper and lower limits • Determined by the surface area to Volume ratio. • Surface area must allow for adequate exchange of nutrients. – Cells that must be large have unique shapes • To maintain a suitable size cells divide • To maintain a suitable size cells must divide – Must be coordinated • Example – If a cell doubles in size before dividing, daughter cells will be twice as large as original cell – eventually cells too large to survive