Student Exploration Cell Division

Name: Date: Student Exploration: Cell Division Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes. Vocabulary: cell division, centriole, centromere, chromatid, chromatin, chromosome, cytokinesis, DNA, interphase, mitosis Prior Knowledge Questions 1. Cells reproduce by splitting in half, a process called cell division. What do cells need to do between divisions to make sure that they don’t just get smaller and smaller? They need to grow. 2. The genetic information of a cell is carried in its DNA (short for deoxyribonucleic acid). What do cells need to do between divisions to make sure that a full set of DNA gets passed on to each daughter cell? They need to make two sets. Warm-up 1. Look at the cells. Do they all look the same? No 2. 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. A. Of the 100 cells shown, how many are in the process of dividing? Maybe 17 B. Select the BAR CHART tab, and turn on Show numerical values. How many cells are in the interphase stage of their life cycle? about 77 C. Based on these two observations, would you say that a cell spends most of its life cycle in interphase or in mitosis/cytokinesis? Activity A: Phases of the cell cycle Interphase ● 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? 1. 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? It goes through many stages. 2. Summarize: On the DESCRIPTION pane, read about each phase in the cell cycle. sketch the cell in each phase and summarize what occurs in your own words. Interphase Sketch In the spaces below, Summary Prophase Cells grow and make more DNA to get ready for Mitosis. Metaphase The cell starts Mitosis by forming chromosomes and spindle fibers move to each end. Anaphase The chromosomes line up in the center of the cell and the spindle fibers attach to the chromosomes. Telophase The spindle fibers then pull, splitting the chromosomes in half. Cytokinesis A membrane forms around the daughter chromosomes and the nucleolus appears in the nucleus. Interphase The membrane goes inward forming two cells. 2. Analyze: Use your summaries and the Gizmo to answer the following questions: A. What are the four phases of mitosis? Prophase Metaphase Anaphase Telophase B. During which phase is the DNA duplicated? Interphase C. What is the relationship between chromatin and chromosomes? Chromatin makes up chromosomes. D. In which phase are chromatids pulled apart? Anaphase E. What is the role of the centrioles? To organize microtubes F. In which phase does a new nuclear membrane develop? Telophase G. A cell has a single line of chromosomes. What is the phase? Metaphase H. During which three phases are individual chromosomes no longer visible? Anaphase Telophase Cytokinesis 3. Think and discuss: Why is it important that the cell’s DNA is duplicated before cell division? So it can pass on copies to the daughter cell. 4. 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. 46 because when they split, each cell will need to have one half of each of the chromosomes. All Activity B: ● Click Reset. ● Select the TABLE tab. Duration of phases Question: What is the relative duration of each phase of the cell cycle? 1. 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 Interphase Prophase Metaphase Anaphase Telophase Cytokinesis 1 88 8 2 1 1 0 2 80 11 3 2 2 2 3 79 10 3 2 3 3 4 79 9 4 1 3 4 Avg. 81.5 9.5 2.25 2.25 3 1.5 2. Analyze: Which phase of the cell cycle is longest? Interphase Shortest? Anaphase Explain your answers: Most of the cells were in interphase meaning that it is the longest phase and barely any were in anaphase with one trial having one, so it is the shortest 3. Calculate: You can use your data to estimate the duration of each phase of the cell cycle. For example, if 8% of the cells were in prophase and the cell cycle was 10 hours long, then prophase would last 8% of 10 hours, or 0.8 hours (48 minutes). Use percentages to estimate the duration of each phase of the cell cycle. Show your work. Interphase: 490 minutes Prophase: 50 minutes Metaphase: 20 minutes Anaphase: 14 minutes Telophase: 13 minutes Cytokinesis: 12 minutes Reproduction for educational use only Extension: Cell populations ● Click Reset. ● Select the GRAPH tab. ● Set the Cycle Length to 5 hours. Question: How quickly do cells multiply? 1. 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.) Either hand draw in the graph or edit using the drawing tools. What is the general shape of the graph? At first it is slow but it then grows very fast. 2. Analyze: Look closely at the graph. A. About how long did it take to grow the first 20 cells? About a day. B. How long did it take to grow the last 20 cells? About an hour. C. Would you say the rate of cell growth is increasing or decreasing? Explain. Increasing because it started out very slow but increased. 3. Extend your thinking: In living organisms, the cell cycle is closely regulated. What do you think will happen if cell division is not controlled? The cells would start getting out of control.