10 2 Cell Division Copyright Pearson Prentice Hall

10 -2 Cell Division Copyright Pearson Prentice Hall

The larger the cell becomes, the more demands the cell places on its DNA and the more trouble the cell has moving enough nutrients and wastes across the cell membrane. DNA "Overload" – In time as the cell grows larger; the DNA can no longer serve its increasing needs Surface Area- to- Volume Ratio Volume increases faster than the surface area of a growing cell The surface area-to-volume will decrease. (causes problems)

So, surface area to volume is why the cells of an organism do not grow larger even though the organism grows much larger and why cells stay small. To stay small, cells must reproduce. 2 Basic Types of Reproduction Asexual reproduction one parent; offspring is identical to parent Sexual reproduction two parents; offspring is not identical to parents

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

Chromosomes Copyright Pearson Prentice Hall

Chromosomes Each chromosome consists of two identical “sister” chromatids. Sister chromatids Each pair of chromatids is attached at an area called the centromere. Centromere Copyright Pearson Prentice Hall

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

The 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

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

The Cell Cycle The cell cycle consists of four phases: • G 1 (First Gap Phase) • S Phase • G 2 (Second Gap Phase) • M Phase Copyright Pearson Prentice Hall

Events of the Cell Cycle Copyright Pearson Prentice Hall

Mitosis Summary (IPMAT) 2 N 2 N 2 N diploid cell –Two copies of each chromosome. Where do the two copies come from? ? 2 identical diploid daughter cells formed

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

Mitosis Copyright Pearson Prentice Hall

Mitosis Section 10 -2 Spindle forming Prophase Centromere Click to Continue Copyright Pearson Prentice Hall Chromosomes (paired chromatids)

Mitosis Spindle forming 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

Mitosis 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. Spindle forming Centromere Chromosomes (paired chromatids) Copyright Pearson Prentice Hall

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

Mitosis Metaphase Centriole Spindle Centriole Metaphase Click to Continue 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

Mitosis Anaphase Individual chromosomes Anaphase Copyright Pearson Prentice Hall

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

Mitosis Telophase Nuclear envelope reforming Telophase Copyright Pearson Prentice Hall

Mitosis 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

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

Cytokinesis 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

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

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

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

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

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

10 -2 DNA replication takes place during the a. S phase of the cell cycle. b. G 1 phase of the cell cycle. c. G 2 phase of the cell cycle. d. M phase of the cell cycle. Copyright Pearson Prentice Hall

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

END OF SECTION

10 -3 Regulating the Cell Cycle Copyright Pearson Prentice Hall

Controls on Cell Division Experiments show that normal cells will reproduce until they come into contact with other cells. When cells come into contact with other cells, they respond by not growing. This demonstrates that controls on cell growth and division can be turned on and off. Copyright Pearson Prentice Hall

Cell Cycle Regulators The cell cycle is regulated by a specific protein. The amount of this protein in the cell rises and falls in time with the cell cycle. Scientists called this protein cyclin because it seemed to regulate the cell cycle. Copyright Pearson Prentice Hall

Uncontrolled Cell Growth Cancer is a disorder in which some of the body's own cells lose the ability to control growth. How are cancer cells different from other cells? Copyright Pearson Prentice Hall

Uncontrolled Cell Growth Cancer cells do not respond to the signals that regulate the growth of most cells. Copyright Pearson Prentice Hall

Uncontrolled Cell Growth Cancer cells divide uncontrollably and form masses of cells called tumors that can damage the surrounding tissues. Cancer cells may break loose from tumors and spread throughout the body, disrupting normal activities and causing serious medical problems or even death. Copyright Pearson Prentice Hall

10 -3 The cell cycle is believed to be controlled by proteins called ● spindles. ● cyclins. ● regulators. ● centrosomes. Copyright Pearson Prentice Hall

10 -3 Proteins that respond to events inside the cell are called ● internal regulators. ● external regulators. ● cyclins. ● growth factors. Copyright Pearson Prentice Hall

10 -3 Once a multicellular organism reaches adult size, the cells in its body ● stop dividing. ● grow and divide at different rates, depending on the type. ● have the same life span between cell divisions. ● undergo cell division randomly. Copyright Pearson Prentice Hall

10 -3 One effect of an internal regulator is that a cell will not begin mitosis until ● it becomes too large. ● the cell’s growth is stimulated. ● it is in physical contact with other cells. ● all its chromosomes have been replicated. Copyright Pearson Prentice Hall

10 -3 One factor common to almost all cancer cells is ● a lack of cyclin. ● a defect in gene p 53. ● exposure to tobacco smoke. ● exposure to radiation. Copyright Pearson Prentice Hall

END OF SECTION