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October 31, 2013 Take out your Cell Division: Mitosis foldable. Turn in your Reinforcement. At your table, make two stacks: One for vocab One for PowerNotes Ms. Clark will come around and stamp them later in class. Model of the Cell Cycle You will work in pairs to model the cell cycle. Instructions are on your table. Read the instructions completely before starting the activity. Leave some space below/around your drawings. Cell Cycle Cell cycle can be broken down into three major parts: Cells divide at different rates. Interphase (maintenance and growth) Mitosis (nuclear division) Cytokinesis (cytoplasmic division) Some cells enter a G0 phase. Cells in G0 carry on normal functions but are unlikely to divide. Cells will not divide if they live in an environment which: Lacks essential nutrients, or Is too crowded/dense. Nuclear membrane Chromatin Centrioles Interphase Cells spend about 90% of their life in interphase. Purpose of interphase is to: Have cells carry out their normal functions. Prep cells for division. 1. 2. Chromosomes in the nucleus exist in loose threads of DNA and protein called chromatin. Interphase Interphase contains three stages: Gap 1 Synthesis Gap 2 Interphase Gap 1 (G1): Cell carries out its normal functions. Cell grows and replicates its organelles. Interphase Synthesis (S): Cell makes a copy of its DNA. Interphase Gap 2 (G2): Cell continues to carry out normal functions. Additional growth occurs. Nuclear membrane Sister chromatid Spindle fibers Centrioles Prophase Chromosomes condense at the start of mitosis, during prophase. Chromatin condenses into thick rods called chromatid. Prophase Each chromosome in a cell was replicated during interphase. The two identical chromatids are called sister chromatids. Sister chromatids are held together at the centromere. Prophase Prophase At the same time, the nuclear envelope begins to break down. Centrioles, organelles that assist cell division, begin to migrate to opposite sides of the cell. Spindle fibers grow from the centrioles and radiate to the center of the cell. Prophase Centrioles Spindle fibers Centromere Sister chromatid Metaphase Spindle fibers attach to each pair of sister chromatids at their centromere. The fibers help move the chromosomes to the middle of the cell. Metaphase Spindle fibers Centrioles Individual, identical chromosomes Anaphase During anaphase, sister chromatids separate from each other. Spindle fibers begin to shorten, pulling the identical chromatids toward opposite sides of the cell. Before Anaphase Spindle fiber Chromosome Centromere After Anaphase Anaphase Nuclear membrane Cleavage furrow Individual, identical chromosomes Centrioles Telophase Once the complete set of identical chromosomes reach opposite ends of the cell: A nuclear membrane begins to form around each set of chromosomes. The chromosomes begin to uncoil out of their tightly-packed form (chromatid) into their loosely-packed form (chromatin). The spindle fibers fall apart. Telophase Telophase Interphase is the growth and maintenance stage of a cell. Mitosis is the division of the cell nucleus and its contents. Stages of mitosis = PMAT Telophase mitosis. marks the end of Telophase Nuclear membrane Chromatin Identical daughter cells Centrioles Cytokinesis Cytokinesis is the division of the cell’s Cytokinesis marks the end of cell division. cytoplasm. Cytokinesis Each new cell is called a daughter cell They are genetically identical to each other. The daughter cells enter interphase and begin the cell cycle again. Cytokinesis Cytokinesis differs in animal and plant cells. In animal cells, the cell membrane forms a cleavage furrow. The daughter cells gradually move apart until their membranes pinch close. In plant cells, a cell plate grows between the two nuclei. Model of the Cell Cycle Work with your partner to determine the most important points of each phase in the cell cycle. Write bullet points briefly describing this information. Homework Section Vocab PowerNotes Reinforcement Section 5.3: 5.5: Vocab PowerNotes Reinforcement Exit Question What are the four stages of mitosis?
