Copyright Pearson Prentice Hall 10-2 Cell Division Photo Credit: © CAMR/A.B. Dowsett/Science Photo Library/Photo Researchers, Inc. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Cell Division In eukaryotes, cell division occurs in two major stages. The first stage, division of the cell nucleus, is called mitosis. The second stage, division of the cell cytoplasm, is called cytokinesis. Copyright Pearson Prentice Hall

Chromosomes Chromosomes Genetic information is passed from one generation to the next on chromosomes. Before cell division, each chromosome is duplicated, or copied.

Copyright Pearson Prentice Hall Chromosomes Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Chromosomes Each chromosome consists of two identical “sister” chromatids. Each pair of chromatids is attached at an area called the centromere. Sister chromatids Photo Credit: © Gunther F. Bahr/AFIP/Stone Centromere Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Chromosomes When the cell divides, the chromatids separate. Each new cell gets one chromatid. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Cell Cycle Cell Cycle The cell cycle is the series of events that cells go through as they grow and divide. Interphase is the period of growth that occurs between cell divisions. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Cell Cycle During the cell cycle: a cell grows prepares for division divides to form two daughter cells, each of which begins the cycle again Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall The Cell Cycle The cell cycle consists of four phases: G1 (First Gap Phase) S Phase G2 (Second Gap Phase) M Phase Copyright Pearson Prentice Hall

Events of the Cell Cycle During G1, the cell increases in size synthesizes new proteins and organelles Copyright Pearson Prentice Hall

Events of the Cell Cycle During the S phase, chromosomes are replicated DNA synthesis takes place Once a cell enters the S phase, it usually completes the rest of the cell cycle. Copyright Pearson Prentice Hall

Events of the Cell Cycle The G2 Phase (Second Gap Phase) organelles and molecules required for cell division are produced Once G2 is complete, the cell is ready to start the M phase—Mitosis Copyright Pearson Prentice Hall

Events of the Cell Cycle During the cell cycle, the cell grows, replicates its DNA, and divides into two daughter cells. DNA synthesis takes place during the S phase. Cell division takes place during the M phase. G1 and G2 are gap phases. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Mitosis Mitosis Biologists divide the events of mitosis into four phases: (PMAT) Prophase Metaphase Anaphase Telophase Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Mitosis Most eukaryotic cells go through a regular cycle of interphase, mitosis and cytokinesis. Mitosis has four phases: Prophase, Metaphase, Anaphase and Telophase. The events shown here are typical of animal cells. Mitosis Copyright Pearson Prentice Hall

Chromosomes (paired chromatids) Mitosis Section 10-2 Spindle forming Prophase Prophase Chromosomes (paired chromatids) Centromere Most eukaryotic cells go through a regular cycle of interphase, mitosis and cytokinesis. Mitosis has four phases: Prophase, Metaphase, Anaphase and Telophase. The events shown here are typical of animal cells. Click to Continue Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Mitosis Spindle forming Prophase Prophase is the first and longest phase of mitosis. The centrioles separate and take up positions on opposite sides of the nucleus. Centromere Chromosomes (paired chromatids) Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Mitosis Spindle forming The centrioles lie in a region called the centrosome. The centrosome helps to organize the spindle, a fanlike microtubule structure that helps separate the chromosomes. Centromere Chromosomes (paired chromatids) Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Mitosis Spindle forming Chromatin condenses into chromosomes. The centrioles separate and a spindle begins to form. The nuclear envelope breaks down. Centromere Chromosomes (paired chromatids) Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Mitosis Metaphase Centriole Spindle Centriole Metaphase Click to Continue Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Mitosis Centriole Metaphase The second phase of mitosis is metaphase. The chromosomes line up across the center of the cell. Microtubules connect the centromere of each chromosome to the poles of the spindle. Spindle Copyright Pearson Prentice Hall

Individual chromosomes Mitosis Anaphase Individual chromosomes Anaphase Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Mitosis Anaphase Anaphase is the third phase of mitosis. The sister chromatids separate into individual chromosomes. The chromosomes continue to move until they have separated into two groups. Individual chromosomes Copyright Pearson Prentice Hall

Nuclear envelope reforming Mitosis Telophase Nuclear envelope reforming Telophase Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Mitosis Telophase Telophase is the fourth and final phase of mitosis. Chromosomes gather at opposite ends of the cell and lose their distinct shape. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Mitosis A new nuclear envelope forms around each cluster of chromosomes. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Cytokinesis Cytokinesis Cytokinesis Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Cytokinesis During cytokinesis, the cytoplasm pinches in half. Each daughter cell has an identical set of duplicate chromosomes Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall Cytokinesis in Plants In plants, a structure known as the cell plate forms midway between the divided nuclei. Cell plate Cell wall Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 10-2 - or - (must have QuickTake software installed on the computer you are using for this presentation) Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 10-2 The series of events that cells go through as they grow and divide is called the cell cycle. mitosis. interphase. cytokinesis. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 10-2 The phase of mitosis during which the chromosomes line up across the center of the cell is prophase. metaphase. anaphase. telophase. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 10-2 Cytokinesis usually occurs at the same time as telophase. after telophase. during interphase. during anaphase Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 10-2 DNA replication takes place during the S phase of the cell cycle. G1 phase of the cell cycle. G2 phase of the cell cycle. M phase of the cell cycle. Copyright Pearson Prentice Hall

Copyright Pearson Prentice Hall 10-2 During mitosis, “sister” chromatids separate from one another during telophase. interphase. anaphase. metaphase. Copyright Pearson Prentice Hall

Chapter 10 Regulation of the Cell Cycle

Interest Grabber Answers Knowing When to Stop Suppose you had a paper cut on your finger. Although the cut may have bled and stung a little, after a few days, it will have disappeared, and your finger would be as good as new. 1. How do you think the body repairs an injury, such as a cut on a finger? The cut is repaired by the production of new cells through cell division. 2. How long do you think this repair process continues? Cell division continues until the cut is repaired. 3. What do you think causes the cells to stop the repair process? Students will likely say that when the cut is filled in, there is no room for more cells to grow.

Control of Cell Division Section 10-3 If center cells are removed, cells near the space will start to grow again. SHOWS: Cell division genes can be turned on and off Cells grow until they touch other cells

CELL DIVISION GENES Cells near injury are stimulated to divide to heal and replace damaged/missing cells and shut off when the repair has been made.

CELL DIVISION GENES Some cells divide frequently (some human skin cells divide once/hour) Some cells divide occasionally (liver cells divide about once/year) Some cells don’t divide once they form (nerve cells)

CELL CYCLE REGULATORS In early 1980’s scientists discovered a protein in dividing cells that caused a ______________to form in _______________ cells Mitotic spindle NON-dividing Pearson Education Inc; Publishing as Pearson Prentice Hall

CELL CYCLE REGULATORS Levels of this protein rose and fell with the cell cycle so it was named __________ because it seemed to control the cell cycle. A whole family of CYCLINS have since been discovered that regulate the _____________________ in EUKARYOTIC CELLS CYCLIN TIMING of CELL CYCLE Pearson Education Inc; Publishing as Pearson Prentice Hall

OTHER REGULATORS INTERNAL ______________ REGULATORS Proteins that respond to events inside the cell. Allow cell cycle to proceed only if certain processes have happened EX: Cell can’t enter mitosis until all the chromosomes have been copied

OTHER REGULATORS EXTERNAL ______________ REGULATORS Proteins that respond to events outside the cell. Signals tell cell to speed up or slow down the cell cycle EX: Growth factors stimulate cells to divide Especially important during wound healing and embryo development http://www.suite101.com/files/topics/6234/files/tail_HumanTail.gif

EXTERNAL REGULATORS Molecules on the surface of neighboring cells act as signals to slow down or stop the cell’s cycle. These signals prevent excessive growth and keep tissues from disrupting each other. Pearson Education Inc; Publishing as Pearson Prentice Hall

Cancer cells have lost control of their cell division genes SEM Image by: Riedell CHO (Chinese Hamster Ovary) cells in culture

NO CONTACT INHIBITION Cancer cells don’t stop when they touch nearby they just keep growing! That’s what makes a tumor. See a video http://www.exn.ca/news/images/2000/08/02/20000802-cancer.jpg

Cancer cells Don’t stop dividing Like a “car with no brakes” Can spread to new places (METASTASIS) Carcinogens/Mutagens are substances that can damage DNA and cause cancer Ex: Cigarette smoke (OR CHEW), Radiation, chemicals in environment, even viruses, http://www.dfci.harvard.edu/abo/news/publications/pop/fall-winter-2004/images/metastasis_1.jpg