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 pare 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 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
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: G1 (First Gap Phase) S Phase G2 (Second Gap Phase) M Phase Copyright Pearson Prentice Hall Events of the Cell Cycle
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 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 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
Cytokinesis 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 QuickTake 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. G1 phase of the cell cycle. c. G2 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 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 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 cells 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 p53. exposure to tobacco smoke. exposure to radiation. Copyright Pearson Prentice Hall END OF SECTION
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