Cell Division Gizmo Answers

Cell Division Gizmo 2 points each Gizmo Warm-up On the SIMULATION pane of the Cell Division Gizmo™, check that the Cycle Length is set to 12 hours. Click Play ( ), observe until the maximum number of cells is shown, and then click Pause ( ). Look at the cells. Do they all look the same? _____no__________ Cells that are in the process of dividing are said to be in mitosis or cytokinesis. Cells that are not dividing are in interphase. Check the Magnify box and move the cursor over the cells. Of the 100 cells shown, how many are in the process of dividing? __4____________ Select the BAR CHART tab, and turn on Show numerical values. How many cells are in the interphase stage of their life cycle? _______91_______________________ Based on these two observations, would you say that a cell spends most of its life cycle in interphase or in mitosis/cytokinesis? _______interphase________________________ Activity A: Phases of the cell cycle Get the Gizmo ready: • Click Reset ( ). • Select the DESCRIPTION tab. • Click on the right arrow once so that Interphase is shown. Question: What are the stages of the cell cycle? • Observe: Click Play and hold the cursor over the cell. Observe the cell as it divides several times. (This happens quickly!) What do you notice happening during this process? __________The cell will double up with material in it and split into two different cells ___________________________________________________________ • Summarize: On the DESCRIPTION pane, read about each phase in the cell cycle. In the spaces below, sketch the cell in each phase and summarize what occurs in your own words. Phase Sketch Summary Interphase It preparesitself by replicating its genetic information and all of the organelles. All of the preparations are done during the interphase. Interphase proceeds in three stages, G1, S, and G2. Cell division operates in a cycle. Therefore, interphase is preceded by the previous cycle of mitosis and cytokinesis Prophase The chromosomes condense and become visible, the nuclear membrane breaks down, and the spindle apparatus forms at opposite poles of the cell Metaphase n metaphase the tetrads are again arranged across the centre by the movements of the kinetochores with the two centromeres opposite each other, but this time the sister chromatids will not be pulled apart as in mitosis Anaphase In anaphase the chromatids holding the chromosomestogether loosen. The two homologous chromatids of each tetrad are separated into separate poles. Since the chromosomes from each parent can go into either pole this is another means to increase genetic diversity. Telophase In this phase, like in mitosis the chromosomes are moved into opposite poles and the nuclear envelope reforms and the spindle is broken down. Remember that there are two chromosomes, not one as in mitosis. Cytokinesis The cell divides to produce two daughter cells each containing the same number and type of chromosomes as the parent cell Activity A (continued from previous page) • Analyze: Use your summaries and the Gizmo to answer the following questions: • What are the four phases of mitosis? _______prophase________________, _________________metaphase_________________________, ___________telophase___________, ______anaphase_________________ • During which phase is the DNA duplicated? ____Interphase_________________ • What is the relationship between chromatin and chromosomes? ______________ ________During prophase, chromatin condenses to form chromosomes_____________________________________________________ ______ • In which phase are chromatids pulled apart? ___anaphase__________________ • What is the role of the centrioles? ________ Centrioles produce spindle fibresand help toorganize the movement of chromosomes_______________________________ • In which phase does a new nuclear membrane develop? ____telophase_________________ • A cell has a single line of chromosomes. What is the phase? ____metaphase_______________ • During which three phases are individual chromosomes no longer visible? ____cytokinesses________________, ____trelophases_________________, _______interphase_________________ • Think and discuss: Why is it important that the cell’s DNA is duplicated before cell division? ______Because if the cells separate before it copied it will only get half the DNA of the parent’s cell________________________________________________________ ______ • Challenge: Human cells have 46 chromosomes. Each chromosome consists of a pair of identical chromatids attached together by a structure called a centromere. Once the chromosome has split, each chromatid is called a daughter chromosome. At the end of cytokinesis, how many daughter chromosomes will be found in each cell? Explain. ______There will be 46 chromosomes in each daughter cell.________________________________________________________ _______ Activity B: Duration of phases Get the Gizmo ready: • Click Reset. • Select the TABLE tab. Question: What is the relative duration of each phase of the cell cycle? • Collect data: Set the Cycle Length to 10 hours and click Play. Click Pause when the maximum number of cells has been reached. On the TABLE tab, click Record data. Record the number of cells in each phase of the cell cycle in the table below. Then click Play, wait for a while, and click Record data again. Repeat this process until you have recorded four sets of results, and then find the average number of cells in each phase. Trial Interphas e Prophase Metaphas e Anaphase Telophase Cytokinesi s 1 81 9 1 3 2 4 2 87 6 0 2 2 3 3 82 12 0 2 2 2 4 88 4 1 3 1 3 Avg. 84.5 7.7 1 2.5 2 3 • Analyze: Which phase of the cell cycle is longest? __interphase__________ Shortest? ______metaphse______ Explain your answers: Extension: Cell populations Get the Gizmo ready: • Click Reset. • Select the GRAPH tab. • Set the Cycle Length to 5 hours. Question: How quickly do cells multiply? • Collect data: Click Play to start a new simulation. Click Pause when the maximum number of cells is reached. View the total number of cells on the GRAPH tab. (Click the “–” button until the whole graph is visible.) Draw a sketch of this graph here. What is the general shape of the graph? _____The graph stays steady at first then goes higher ____________________________ ___ • Analyze: Look closely at the graph. • About how long did it take to grow the first 20 cells? _____27hr_____________________ • About how long did it take to grow the last 20 cells? _______23hr___________________ • Would you say the rate of cell growth is increasing or decreasing? Explain. _____The rate of cell growth is increasing,its takes about 20 hours to grow 10 ells ,but it only takes2-3 hr to grow the last 20 cells_____________________________________________________ _________ ________________________________________________________ ___________ • Extend your thinking: In living organisms, the cell cycle is closely regulated. What do you think will happen if cell division is not controlled? _____If the cell division is not controlled, it might develop into some new kinds of disease which people can not control.________________________________________________________ ____________ ______________________________________________________________ ___________