What is meant by the "division of the nucleus"? What do you think this colorful picture shows? If you guessed that it s a picture of a cell undergoing cell division, you are right. But more specifically, the image is a lung cell stained with fluorescent dyes undergoing mitosis, during early anaphase. Mitosis and Cytokinesis During mitosis, when the nucleus divides, the two chromatids that make up each chromosome separate from each other and move to opposite poles of the cell. Mitosis actually occurs in four phases. The phases are called prophase, metaphase, anaphase, and telophase. Prophase The first and longest phase of mitosis is prophase. During prophase, chromatin condenses into chromosomes, and the nuclear envelope, or membrane, breaks down. In animal cells, the centrioles near the nucleus begin to separate and move to opposite poles (sides) of the cell. As the centrioles move, a spindle starts to form between them. The spindle, shown in Figure below, consists of fibers made of microtubules. Metaphase During metaphase, spindle fibers attach to the centromere of each pair of sister chromatids (see Figure below). The sister chromatids line up at the equator, or center, of the cell. This is also known as the metaphase plate. The spindle fibers ensure that sister chromatids will separate and go to different daughter cells when the cell divides. Anaphase During anaphase, sister chromatids separate and the centromeres divide. The sister chromatids are pulled apart by the shortening of the spindle fibers. This is like reeling in a fish by shortening the fishing line. One sister chromatid moves to one pole of the cell, and the other sister chromatid moves to the opposite pole. At the end of anaphase, each pole of the cell has a complete set of chromosomes. Telophase During telophase, the chromosomes begin to uncoil and form chromatin. This prepares the genetic material for directing the metabolic activities of the new cells. The spindle also breaks down, and new nuclear membranes (nuclear envelope) form. Cytokinesis Cytokinesis is the final stage of cell division in eukaryotes as well as prokaryotes. During cytokinesis, the cytoplasm splits in two and the cell divides. Cytokinesis occurs somewhat differently in plant and animal cells, as shown in Figure below. In animal cells, the plasma membrane of the parent cell pinches inward along the cell s equator until two daughter cells form. In plant cells, a cell plate forms along the equator of the parent cell. Then, a new plasma membrane and cell wall form along each side of the cell plate.
Read It! Read It! What happens during prophase of mitosis? 2. During which phase of mitosis do sister chromatids separate? Read It! 3. 4. Describe what happens during cytokinesis in animal cells. Read It! If a cell skipped metaphase during mitosis, how might this affect the two daughter cells?
Go to the following Brainpop Video: http://tinyurl.com/px3tx88 2. When do spindle fibers first become visible? A. Telophase B. Metaphase C. Anaphase D. Prophase How does your body grow as you get 3. older? 4. A. Your cells fill with water and get bigger B. Your cells divide, producing new cells C. Your cells elongate D. Your cells combine with one another What is the name of this structure? A. Center B. Centriole C. Centromere D. Centralia
How does the number of chromosomes in a daughter cell compare to the number of 5. chromosomes in a parent cell? A. The daughter cell has 1/2 the number of chromosomes B. The daughter cell has twice the number of chromosomes C. The daughter cell has the exact same number of chromosomes D. The daughter cell has 1/4 the number of chromosomes 6. What are the four stages of mitosis in order? A. Anaphase, prophase, metaphase, telophase B. Prophase, telophase, metaphase, anaphase C. Prophase, multiphase, anaphase, telophase D. Prophase, Metaphase, Anaphase, Telophase What is a chromosome? 7. A. A small piece of a cell membrane 8. B. A pair of DNA molecules C. The protein center of a cell D. Part of the cell s endoplasmic reticulum Where do duplicated chromosomes line up during metaphase? A. Against the wall B. Against the cell membrane C. In the center of the cell D. At either end of the cell
Explore It! Explore It! Go to this Gizmo: Cell Division http://tinyurl.com/jyj4zsq 2. Get the Gizmo ready: If you were playing with the Gizmo, Click Reset ( ). Select the DESCRIPTION tab. Click on the right arrow once so that Interphase is shown. Explore It! Explore It! Question: What are the stages of the 3. cell cycle? 4. 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? Answer the question on your Lab Sheet. Summarize: On the DESCRIPTION pane, read about each phase in the cell cycle. In the table on your lab sheet, sketch the cell in each phase and summarize what occurs in your own words.
Research It! Enrich It! How is the cell cycle/mitosis related to cancer? Go online to find out the link Go to the PLIX located at this site: between cell division and http://tinyurl.com/zs68jpb cancer. Write It! Illustrate It! Explain why cell division is important in your everyday life. What does it do? What would happen if cell division didn t work anymore? Using two different colors for your chromosomes, complete the diagram of the cell cycle; starting with interphase. Draw your chromatin/chromosomes consistently
Assess It! Organize It! Launch the Socrative App or go to www.socrative.com Put the names and pictures of the stages of the cell cycle in order. Match the description of what is happening to the cell during that stage of the cell cycle. Assess It! Organize It! Launch the Socrative App or go to www.socrative.com Put the names and pictures of the stages of the cell cycle in order. Match the description of what is happening to the cell during that stage of the cell cycle.
Chromosomes attach to spindle fibers at their centromere and line up across the middle of the cell. The centromeres split, the chromatids are pulled apart to opposite ends of the cell. The cell stretches out. The chromosomes begin to stretch out, two nuclear membranes appear. Cell membrane pinches in and the cell splits into two. Each daughter cell gets an identical copy of the DNA and about half of the cytoplasm and organelles.
Prophase Metaphase Anaphase Telophase Cytokinesis Cell grows, copies its DNA and prepares to divide. Chromatin condenses to form chromosomes, spindle fibers form a bridge, nuclear membrane disappears.
Credit: 3D4Medical / Universal Images Group Credit: 3D4Medical / Universal Images Group Credit: 3D4Medical / Universal Images Group Credit: 3D4Medical / Universal Images Group Credit: 3D4Medical / Universal Images Group Interphase
Task Card 3: Input Stations: Explore It! What do you notice happening while the cell is dividing? Task Card 1: Read It! Task Card 4: Phase Sketch Summary Task Card 2: Interphase Task Card 3: Prophase Task Card 4: Metaphase 2. 4. 3. 5. 6. 7. 8. Anaphase Research It! Task Card 1: Telophase Cytokinesis
Research It! (Continued) Task Card 1: Illustrate It! Task Card 1: Metaphase Interphase Prophase Cytokinesis Anaphase Output Stations Write It! Telophase Task Card 1: Assess It! (See teacher for Socrative Code) Organize It! Teacher Initials: Reflection: How did you do? What did you find easy? What mistakes did you make?