Exam (elaborations) BIOLOGY 101 Cell Division Gizmos

Exam (elaborations) BIOLOGY 101 Cell Division Gizmos Vocabulary: cell division, centriole, centromere, chromatid, chromatin, chromosome, cytokinesis, DNA, interphase, mitosis Prior Knowledge Questions (Do these BEFORE using the Gizmo.) 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? In between cell division the cells go through the interphase stage. This includes the G1 phase, the S phase and the G2 phase. In the G1 phase the cell is growing and starting to get ready to replicate DNA. In the S phase the DNA is replicated and in the G2 phase the cell prepares to divide. Cells spend most of their life in this stage. 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? The cells have to synthesize (replicate) their DNA which is done in the S phase of interphase. 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 ( ). 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? 22 B. Select the BAR CHART tab, and turn on Show numerical values. How many cells are in the interphase stage of their life cycle? 78 This study source was downloaded by from CourseH on :12:42 GMT -05:00 This study resource was shared via CourseH BIOLOGY 101 Cell Division Gizmos 2018 Sharma 2 C. Based on these two observations, would you say that a cell spends most of its life cycle in interphase or in mitosis/cytokinesis? Most of the cell’s life is spent in interphase This study source was downloaded by from CourseH on :12:42 GMT -05:00 This study resource was shared via CourseH 2018 Sharma 3 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? 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? The cell remains in interphase for 10 out of the 12 hours of the cycle. In the remaining 2 hours I noticed that the nucleus is gone, and the centrioles are moving to opposite sides of the cell. The chromosomes are then pulled apart. Then the chromosomes are pulled apart becoming sister chromatids. Then two new cells are made and the process repeats. 2. 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 Growing of cell and replication of DNA and Organelles. Prophase The nuclear membrane breaks down and the centrioles start to move to opposite ends of the cell. The chromatin becomes chromosomes. Metaphase The chromosomes line up in the middle of the cell and the spindle fibers attach to the centromere of each chromosome. Anaphase The chromosomes are pulled apart by the spindle fibers and are put on opposite sides of the cell. Telophase The nuclear membrane starts to reform, and the This study source was downloaded by from CourseH on :12:42 GMT -05:00 This study resource was shared via CourseH 2018 Sharma 4 chromosomes go back into a chromatin form. Cytokinesis Division of the cytoplasm and cell membrane. Two new cells are formed. Activity A (continued from previous page) 3. 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 are the strands of DNA inside the nucleus and chromosomes appear when the chromatin shrinks from it unraveled state becoming chromosomes. D. In which phase are chromatids pulled apart? Anaphase E. What is the role of the centrioles? To go to opposite ends of the cell, attach to the centromere and pull the chromosomes apart 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? Interphase, telophase, and cytokinesis 4. Think and discuss: Why is it important that the cell’s DNA is duplicated before cell division? If the cells DNA is not duplicated before cell division one of the two daughter cells would not obtain the correct amount of DNA. One of the cells could end up getting it all leaving the other with none or both cells get partial amounts resulting in both cells dying. It is required that DNA is duplicated so once the mitosis is complete each new daughter cell has the right amount of DNA information. This study source was downloaded by from CourseH on :12:42 GMT -05:00 This study resource was shared via CourseH 2018 Sharma 5 5. 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. At the end of cytokinesis there will be 46 daughter chromosomes in each new cell. This is the case because during the anaphase stage of mitosis the original 46 chromosomes are pulled apart by the spindle fibers dividing them in to. This results in 92 daughter chromosomes in the cell. Next each set of 46 chromosomes is taken to its own side of the cell and mitosis continues which results in 2 daughter cells each with 23 pairs o