Cell Division

Section 8.2 Summary – pages 201 - 210 Cell Division Cell division is the process by which new cells are produced from one cell. Cell division results in two cells that are identical to the original, parent cell. Section 8.2 Summary – pages 201 - 210

Section 8.2 Summary – pages 201 - 210 Chromosomes Chromosomes are the carriers of the genetic material that is copied and passed from generation to generation of cells. Accurate transmission of chromosomes during cell division is critical. Section 8.2 Summary – pages 201 - 210

Section 8.2 Summary – pages 201 - 210 The structure of eukaryotic chromosomes Sister chromatids Centromere Continued coiling within supercoil Supercoil within chromosome Chromosome DNA Section 8.2 Summary – pages 201 - 210

Section 8.2 Summary – pages 201 - 210 The Cell Cycle The cell cycle is the sequence of growth and division of a cell. The majority of a cell’s life is spent in the growth period known as interphase. Interphase Section 8.2 Summary – pages 201 - 210

Section 8.2 Summary – pages 201 - 210 Interphase: A Busy Time Interphase, the busiest phase of the cell cycle, is divided into three parts. Interphase DNA synthesis and replication Centrioles replicate; cell prepares for division Rapid growth and metabolic activity Section 8.2 Summary – pages 201 - 210

Section 8.2 Summary – pages 201 - 210 The Cell Cycle Following interphase, a cell enters its period of nuclear division called mitosis. Following mitosis, the cytoplasm divides, separating the two daughter cells. Mitosis Section 8.2 Summary – pages 201 - 210

Section 8.2 Summary – pages 201 - 210 The Phases of Mitosis The four phases of mitosis are prophase, metaphase, anaphase, and telophase. Section 8.2 Summary – pages 201 - 210

Section 8.2 Summary – pages 201 - 210 Prophase: The first phase of mitosis During prophase, the chromatin coils to form visible chromosomes. Spindle fibers Disappearing nuclear envelope Doubled chromosome Section 8.2 Summary – pages 201 - 210

Section 8.2 Summary – pages 201 - 210 Prophase: The first phase of mitosis The two halves of the doubled structure are called sister chromatids. Sister chromatids Section 8.2 Summary – pages 201 - 210

Section 8.2 Summary – pages 201 - 210 Prophase: The first phase of mitosis Sister chromatids are held together by a structure called a centromere, which plays a role in chromosome movement during mitosis. Centromere Section 8.2 Summary – pages 201 - 210

Section 8.2 Summary – pages 201 - 210 Metaphase: The second stage of mitosis During metaphase, the chromosomes move to the equator of the spindle. Centromere Sister chromatids Section 8.2 Summary – pages 201 - 210

Section 8.2 Summary – pages 201 - 210 Anaphase: The third phase of mitosis During anaphase, the centromeres split and the sister chromatids are pulled apart to opposite poles of the cell. Section 8.2 Summary – pages 201 - 210

Section 8.2 Summary – pages 201 - 210 Telophase: The fourth phase of mitosis During telophase, two distinct daughter cells are formed. The cells separate as the cell cycle proceeds into the next interphase. Nuclear envelope reappears Two daughter cells are formed Section 8.2 Summary – pages 201 - 210

Section 8.2 Summary – pages 201 - 210 Cytokinesis Following telophase, the cell’s cytoplasm divides in a process called cytokinesis. Cytokinesis differs between plants and animals. Toward the end of telophase in animal cells, the plasma membrane pinches in along the equator. Section 8.2 Summary – pages 201 - 210

Section 8.2 Summary – pages 201 - 210 Cytokinesis Plant cells have a rigid cell wall, so the plasma membrane does not pinch in. A structure known as the cell plate is laid down across the cell’s equator. A cell membrane forms around each cell, and new cell walls form on each side of the cell plate until separation is complete. Section 8.2 Summary – pages 201 - 210

Section 8.2 Summary – pages 201 - 210 Results of Mitosis When mitosis is complete, unicellular organisms remain as single cells. In multicellular organisms, cell growth and reproduction result in groups of cells that work together as tissue to perform a specific function. Section 8.2 Summary – pages 201 - 210

Section 8.2 Summary – pages 201 - 210 Results of Mitosis Tissues organize in various combinations to form organs that perform more complex roles within the organism. Multiple organs that work together form an organ system. Section 8.2 Summary – pages 201 - 210

Questions

Question 1 Question 1 The stringy structures in the cell nucleus that contain DNA are __________. A. centromeres B. chromosomes C. genes D. chlorophylls Section 2 Check

Question 2 Look at the diagram and identify the stage of mitosis that is depicted. Centromere Sister chromatids A. prophase C. anaphase B. metaphase D. telophase Section 2 Check

Question 3 What is the process by which a cell's cytoplasm divides? A. cytokinesis B. telekinesis C. meiosis D. mitosis Section 2 Check

Question 4 In multicellular organisms, groups of cells that work together to perform a specific function are called __________. A. organ systems B. organs C. tissues D. cell cycles Section 2 Check

Control of the Cell Cycle

Section 8.3 Summary – pages 211 - 213 Proteins and enzymes control the cell cycle The cell cycle is controlled by proteins called cyclins and a set of enzymes that attach to the cyclin and become activated. Occasionally, cells lose control of the cell cycle. Section 8.3 Summary – pages 211 - 213

Section 8.3 Summary – pages 211 - 213 Normal Control of the Cell Cycle This uncontrolled dividing of cells can result from the failure to produce certain enzymes, the overproduction of enzymes, or the production of other enzymes at the wrong time. Cancer is a malignant growth resulting from uncontrolled cell division. Section 8.3 Summary – pages 211 - 213

Section 8.3 Summary – pages 211 - 213 Cancer: A mistake in the Cell Cycle Currently, scientists consider cancer to be a result of changes in one or more of the genes that produce substances that are involved in controlling the cell cycle. Cancerous cells form masses of tissue called tumors that deprive normal cells of nutrients. Section 8.3 Summary – pages 211 - 213

Section 8.3 Summary – pages 211 - 213 Cancer: A mistake in the Cell Cycle In later stages, cancer cells enter the circulatory system and spread throughout the body, a process called metastasis, forming new tumors that disrupt the function of organs, organ systems, and ultimately, the organism. Section 8.3 Summary – pages 211 - 213

Section 8.3 Summary – pages 211 - 213 The causes of cancer The causes of cancer are difficult to pinpoint because both genetic and environmental factors are involved. Section 8.3 Summary – pages 211 - 213

Section 8.3 Summary – pages 211 - 213 The causes of cancer Environmental factors, such as cigarette smoke, air and water pollution, and exposure to ultraviolet radiation from the sun, are all known to damage the genes that control the cell cycle. Section 8.3 Summary – pages 211 - 213

Section 8.3 Summary – pages 211 - 213 The causes of cancer Cancer may also be caused by viral infections that damage the genes. Section 8.3 Summary – pages 211 - 213

Chapter 8 Questions

Question 3 Magnification of a plant cell reveals centromeres that have split and sister chromatids being pulled to opposite poles of the cell. This cell is in which phase of mitosis? A. prophase B. metaphase C. anaphase D. telophase Chapter Assessment

Disappearing nuclear envelope Question 4 Which phase of mitosis is depicted in this diagram? Spindle Fibers Doubled chromosome Disappearing nuclear envelope A. prophase C. anaphase B. metaphase D. telophase Chapter Assessment

Question 5 What is the term used for the period of the cell cycle represented by the red arrow in this graph? A. prophase DNA synthesis and replication B. metaphase Centrioles replicate; cell prepares for division Rapid growth and metabolic activity C. centrophase D. interphase Chapter Assessment

Question 6 What is the level of organization that is missing in this diagram? Organ Cell Organ System Organism ? (muscle cell) (stomach) (digestive tissue) (Florida Panther) A. mass C. tissue B. cluster D. cycle Chapter Assessment

Question 7 Which structure represents a cell in prophase of mitosis? B C D A. A C. C B. B D. D Chapter Assessment