Gummy worm mitosis worksheet answer key

LAB 7: MITOSIS + MEIOSIS NAME: MOHAMMAD SAIF OBJECTIVES • • • • • Describe the phases of the cell cycle and explain how cells undergo division through mitosis Recognize how carcinogens cause DNA mutations, changing the function of genes which may lead to the development of cancer. Describe differences between normal tissues and cancerous tissues. Distinguish between mitosis and meiosis Describe how meiosis creates genetic variability in gametes THE CELL CYCLE + MITOSIS The cell cycle is composed of several phases: G1 phase, S phase, G2 phase, and mitosis and cytokinesis. Mitosis is the process by which a single parent cell, e.g. a skin cell, divides to create to identical daughter cells, each containing the same number of chromosomes as the parent cell. Mitosis is necessary to create new cells as cells age, are damaged, or become old. Before a cell can divide by mitosis, it must first make a copy of its DNA and its organelles, which are then divided to create two identical daughter cells. Figure 1: The cell cycle illustrating how cells reproduce (By Genomics Education Programme - The cell cycle, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=50542843) G1 phase: the cell needs to enlarge to accommodate the replicated genetic material and other organelles in the cell. Additional cytoplasm is also produced. S phase: exact copies of the cells chromosomes are created. G2 phase: cell can make final preparations in order to enter mitosis. M-phase: Mitosis begins with the condensation of the chromosomes. This creates tightly compacted chromosomes which can be seen under the microscope. When a chromosome compacts, the two copies of the chromosome are linked, forming an “X” shape. Each copy of the chromosome in the “X” is a sister chromatid. Once the Page 1 of 8 LAB 7: MITOSIS + MEIOSIS chromosomes have compacted, the nuclear membrane will break down. Once the nuclear membrane has broken down, the chromosomes are free to travel to the middle of the cell. They line up in the middle of the cell at the mitotic plate. Microtubules form from the poles of the cell and attach to each chromosome where the sister chromatids meet. Next the microtubules shorten, pulling the sister chromatids apart, each moving to an opposite pole of the cell. Once they have reached the poles of the cell, the two nuclei form around the sister chromatids, and the cell undergoes cytokinesis, forming two daughter cells that have identical DNA. Almost all the cells in your body were produced by mitosis. Mitosis ensures that the daughter cells produced after the division of the cell have one copy of each of the 23 pairs of chromosomes (46 total). These pairs are called homologous chromosomes, because the chromosomes are very similar; they are the same size and possess the same genes. Because every human cell contains 2 copies of each chromosome, humans are diploid organism, which can be abbreviated as 2n. In contrast, the strawberries you worked with earlier have 8 copies of each chromosome, so they are 8n. ✓ WATCH THE FOLLOWING LESSON ON MITOSIS: https://tinyurl.com/o33nr9c (phases of mitosis Bozeman science) ✓ ACTIVITY: Yummy GUMMY ORGANISM 1) Materials needed: Packet of gummy worms Paper plates Markers Each gummy worm represents a chromosome. In your GUMMY ORGANISM, its entire genome (all its DNA) is contained in a single chromosome. GUMMY ORGANISMS are diploid, which means that a regular cell in G1 will have 2 chromosomes. Use diagrams from your textbook to help you to construct the following simulation. 1) Label paper plates: Prophase, Metaphase, Anaphase, Telophase, New Cell 1, New Cell 2. 2) Draw a circle with dashed lines (representing the nucleus dissolving), on the “Prophase plate”. Take two differently colored worms (e.g. one red/blue and one yellow/green) place in the nucleus. This represents a cell in G1 that has two chromosomes, each with a single chromatid. The cell is diploid (2n, because it has 2 copies of the genome). For a cell to be ready to enter Mitosis, you will need to duplicate your DNA. To represent this, take an additional red/blue and yellow/green from your packet, and place each next to the matching chromosomes on the “Prophase plate” 3) Prophase: Take a photo of the Prophase plate 4) Metaphase: Draw a dashed line across the plate (representing the mitotic plates). Line up your 2 pairs of chromosomes at the mitotic plate. Take a photo. Page 2 of 8 LAB 7: MITOSIS + MEIOSIS 5) Anaphase: Separate the two red/blue worms, and the two green/yellows, so you can see that one red/blue, and one green/yellow set is moving towards one pole, and the other set is moving in the opposite directions. You can draw centrioles and the mitotic spindle. Take a photo. 6) Telophase: Place one red/blue and one green/yellow chromosome and place on one side of the cell, and draw a dotted circle (representing a newly forming nucleic membrane). Repeat for the other side of the cell. Two new nuclei are forming. Take a photo. 7) New cells: on each plate, draw a solid circle (representing a nucleus). In the nucleus of each, place one red/blue and one green/yellow chromosome (two diploid 2n cells). Take a photo. 8) Eat the remaining gummies, or share them with your friends. INSERT YOUR LABELLED PHOTO SEQUENCE HERE  ✓ Mitosis Questions 1. At what stage in the cell cycle is DNA synthesized? 2. At what stage of the cell cycle do the cells divide? 3. If a cell undergoing mitosis has 4 chromosomes, how many chromosomes will each of the daughter cells have? 4. At what stage of mitosis do the chromosomes first become visible? 5. What would a cell look like if it underwent mitosis but not cytokinesis? Provide a drawing. 6. Identify the stage of mitosis for each of the following images: A:______________ B:______________ Page 3 of 8 LAB 7: MITOSIS + MEIOSIS Page 4 of 8 LAB 7: MITOSIS + MEIOSIS UNREGULATED CELL CYCLE Cancer is a disease that results from unregulated cell division. This unregulated cell division may result in the formation of masses of cells called tumors, which can be benign or malignant.