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Cell Cycle & Mitosis Fill in your notes sheet with the BOLD words! Chromosomes Chromosomes X-shaped packages made up of DNA and proteins DNA carries the information Proteins are the scaffolding The only time chromosomes are visible is during cell division when they take the form of chromatin. Humans 46 total chromosomes or 23 pairs. Of these pairs, 1 pair are the sex chromosomes which determine gender! Why are cells so small?? Cells must be small to allow materials to get in and out quickly. The bigger a cell, the slower it works! Cell Cycle The 1. 2. 3. period where a cell will: Grow Prepare for division by making molecules, organelles, etc. Divide to form two “daughter” cells Each new “daughter cell” will start the cycle over again. Cell Cycle Cell cycle can be divided into two main sections: Interphase 3 Stages: 1. 2. 3. G1 S G2 (Gap 1) (Synthesis) (Gap 2) Mitosis Otherwise known as cell division Interphase: G1 DNA takes the form of chromatin Nuclear membrane is present – this means we can’t see what’s inside! The nucleolus is visible Interphase: S, G2 S DNA is replicated. We get 2 complete, identical strands of DNA – one for each new cell. G2 Organelles and molecules necessary for cell division are made. Mitosis Prophase Nuclear membrane and nucleolus disintegrate Centrioles move toward opposite sides of the cell and make spindle fibers Chromatin becomes chromosomes, we can now see them. They start to move to the middle of the cell. Metaphase Chromosomes line up in the middle of the cell. We can see this phase easily! Anaphase Centrioles send out spindle fibers to grab onto the middle to the chromosomes. They pull them apart, sending one half of each chromosome (called chromatids) to opposite sides of the cell. Telophase Chromatids reach opposite sides of the cell. Centrioles and spindle fibers disappear. Nuclear membrane and nucleolus reappear. Chromosomes uncoil back into chromatin Cytokinesis Cytoplasm is divided between cells In animals, new cell membranes form In plants, a cell plate forms The result: two offspring cells – each an identical copy of the parent cell Prophase Interphase The Cell Cycle Cytokinesis Metaphase Anaphase Telophase
