Chapter 2, Section 5 Cell Division

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Chapter 2, Section 5 Cell Division Powered By Docstoc
					Chapter 2, Section 5
       Cell Division
Thursday, October 22, 2009
            Pages 72 -- 79
Objectives
 Understand the events that take place
 during the three stages of the cell cycle.
 Understand the role of DNA replication.
 Know the role of nitrogen bases.
Vocabulary Words
 Cell Cycle    Chromosomes
 Interphase    Chromatid
 Replication   Cytokinesis
 Mitosis       Daughter cells
               Centromere
The Cell Cycle
                                          The cell cycle is a
                                          sequence of growth
                                          and division that
                                          cells undergo.
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                                          The cell cycle is
                                          divided into three
                                          main stages.
 Interphase
                                         Interphase is the first
                                         stage of the cell cycle.
                                         The cell grows to its
                                         mature size.
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                                         The cell prepares to
                                         divide into two cells.
Mitosis
                                          Mitosis occurs in 4
                                          phases.
                                            Prophase
                                            Metaphase
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                                            Anaphase
                                            Telophase
Prophase
                                         The threadlike
                                         chromatin in the
                                         nucleus begins to
                                         condense into tiny rods.
                                         Doubled rods of
                                         condensed chromatin is
                                         called chromosome.
                                         Each “leg” of the
                                         chromosome is called a
                                         chromatid.
                                         The centromere holds
                                         the two strands
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                                         together.
Metaphase
                                         Second stage of
                                         mitosis.
                                         The chromosomes
                                         line up in the center
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                                         the spindle fibers.
Anaphase
                                        Centromeres split and
                                        the chromatids
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                                        Chromatids move
                                        toward opposite poles
                                        along the spindle fiber.
                                        A complete set of
                                        chromosomes has
                                        assembled at each pole
                                        at the end of anaphase.
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Telophase
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                                         Nuclei begin to
                                         form at opposite
                                         poles.
                                         Chromatin fibers of
                                         chromosomes
                                         uncoil.
                                         DNA on one cell
                                         have been divided
                                         equally into two.
                                         Telophase ends
                                         mitosis.
Cytokinesis
 Completes the process of cell division.
 Cytoplasm divides and distributes the
 organelles into each of the two new cells.
 Each daughter cell has the same number of
 chromosomes as the original parent cell.
 At the end of cytokinesis, each cell enters
 interphase and the cycle begins again.
Length of Cell Cycle
 The time it takes a cell to go through
 one cell cycle depends on the type of
 the cell.
 The length of each stage in the cell
 cycle also varies.
DNA Ladder
 The ladder is made up of alternating
 sugar and phosphate molecules.
 Each rung is made up of a pair of
 molecules called nitrogen bases.
 4 kinds of nitrogen bases:
   Adenine, thymine, guanine, and cytosine.
   A-T and G-C
The Replication Process
 DNA replication begins when the 2
 sides of the DNA molecule unwind and
 separate.
 The nitrogen bases then pair up on
 each half of the DNA molecule.
 The order will be identical to that of the
 original DNA molecule.
Homework
 Workbook Chapter 2, Section 5 -- due
 10/26.
 Vocabulary quiz 2.5 on 10/26.

				
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