Chapter 8

Cell DivisionSection 8.2 Summary pages 201 - 210Cell DivisionCell 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 - 210ChromosomesChromosomes 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 - 210The structure of eukaryotic chromosomes

CentromereChromosomeSister chromatidsSupercoil within chromosomeContinued coiling within supercoilDNASection 8.2 Summary pages 201 - 210The Cell CycleThe cell cycle is the sequence of growth and division of a cell.The majority of a cells life is spent in the growth period known as interphase.

InterphaseSection 8.2 Summary pages 201 - 210Interphase: A Busy TimeInterphase, the busiest phase of the cell cycle, is divided into three parts.

DNA synthesis and replicationCentrioles replicate; cell prepares for divisionRapid growth and metabolic activityInterphaseSection 8.2 Summary pages 201 - 210The Cell CycleFollowing interphase, a cell enters its period of nuclear division called mitosis.Following mitosis, the cytoplasm divides, separating the two daughter cells.

MitosisSection 8.2 Summary pages 201 - 210The Phases of MitosisThe four phases of mitosis are prophase, metaphase, anaphase, and telophase.Section 8.2 Summary pages 201 - 210Prophase: The first phase of mitosisDuring prophase, the chromatin coils to form visible chromosomes.

Spindle fibersDisappearing nuclear envelopeDoubled chromosomeSection 8.2 Summary pages 201 - 210Prophase: The first phase of mitosisThe two halves of the doubled structure are called sister chromatids.

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

CentromereSection 8.2 Summary pages 201 - 210Metaphase: The second stage of mitosisDuring metaphase, the chromosomes move to the equator of the spindle.

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

Section 8.2 Summary pages 201 - 210Telophase: The fourth phase of mitosisDuring telophase, two distinct daughter cells are formed. The cells separate as the cell cycle proceeds into the next interphase.

Nuclear envelope reappearsTwo daughter cells are formedSection 8.2 Summary pages 201 - 210CytokinesisFollowing telophase, the cells 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 - 210CytokinesisPlant 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 cells 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 - 210Results of MitosisWhen 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 - 210Results of MitosisTissues organize in various combinations to form organs that perform more complex roles within the organism.Multiple organs that work together form an organ system.QuestionsSection 2 Check The stringy structures in the cell nucleus that contain DNA are __________. Question 1D. chlorophylls C. genes B. chromosomes A. centromeres

Question 1Section 2 Check Look at the diagram and identify the stage of mitosis that is depicted. Question 2D. telophase C. anaphase B. metaphase A. prophase

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

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

Control of the Cell Cycle

Section 8.3 Summary pages 211 - 213The 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.Proteins and enzymes control the cell cycleSection 8.3 Summary pages 211 - 213Normal Control of the Cell CycleCancer is a malignant growth resulting from uncontrolled cell division.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.Section 8.3 Summary pages 211 - 213Cancer: A mistake in the Cell CycleCurrently, 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 - 213Cancer: A mistake in the Cell CycleIn 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 - 213The causes of cancerThe causes of cancer are difficult to pinpoint because both genetic and environmental factors are involved.Section 8.3 Summary pages 211 - 213The causes of cancerEnvironmental 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 - 213The causes of cancerCancer may also be caused by viral infections that damage the genes.Chapter 8 Questions

Chapter AssessmentQuestion 3Magnification 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? D. telophase C. anaphase B. metaphase A. prophase

Chapter AssessmentQuestion 4Which phase of mitosis is depicted in this diagram? D. telophase C. anaphase B. metaphase A. prophase Spindle FibersDisappearing nuclear envelopeDoubled chromosome

Chapter AssessmentQuestion 5What is the term used for the period of the cell cycle represented by the red arrow in this graph?D. interphase C. centrophase B. metaphase A. prophase DNA synthesis and replicationRapid growth and metabolic activityCentrioles replicate; cell prepares for divisionWhat is the level of organization that is missing in this diagram? Chapter AssessmentQuestion 6D. cycle C. tissue B. cluster A. mass

?Cell(muscle cell)Organ(stomach)Organ System(digestive tissue)Organism(Florida Panther)Which structure represents a cell in prophase of mitosis? Chapter AssessmentQuestion 7D. D C. C B. B A. A

ABCD