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CELL CYCLE

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Cell Cycle. Period from the beginning of one cell division to the beginning of the next cell division. Divided into 2 parts: Interphase. Cell Division – PowerPoint PPT presentation

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Title: CELL CYCLE


1
CELL CYCLE
  • Mitosis

2
DNA
  • The cells genetic information is carried by the
    chromosomes which are formed by proteins and DNA.
  • The cells of all organisms have a specific number
    of chromosomes, for example
  • Fruit flys have 8 chromosomes
  • Humans have 46 chromosomes

3
DNA (cont.)
  • In order for the DNA to fit inside the nucleus,
    it must compact itself by coiling
  • When DNA is unwound, it is in long, thin strands
    called chromatin
  • When the DNA is completely compacted it is in the
    form of chromosomes and becomes visible under a
    microscope

4
Chromosomes
  • Before cellular division, each chromosome
    replicates
  • Each chromosome is made up of two identical
    sister chromatids joined by a centromere
  • When the cell divdes, the sister chromatids
    separate and each one passes into one of the two
    new cells

5
Cell Cycle
  • Period from the beginning of one cell division to
    the beginning of the next cell division
  • Divided into 2 parts
  • Interphase
  • Cell Division

6
Cell Cycle
Cell Cycle
Cell Division
Interphase
7
Interphase
  • Occurs between cell divisions
  • Cell prepares all the materials necessary for
    cell growth and prepares it for division
  • Accounts for 90 of the total time in the cell
    cycle
  • Divided into 3 stages
  • G1
  • S
  • G2

8
Cell Cycle
Cell Cycle
Cell Division
Interphase
G1
9
G1
  • Also known as Gap 1
  • Characterized by growth and development

10
Cell Cycle
Cell Cycle
Cell Division
Interphase
G1
S
11
S
  • Also known as the synthesis phase
  • Once the cell enters the S phase it is committed
    to cell division
  • Chromosomes in the nucleus replicate

12
Cell Cycle
Cell Cycle
Cell Division
Interphase
G1
S
G2
13
G2
  • Also known as Gap 2
  • This is the shortest of the 3 phases in
    interphase
  • Cell makes organelles and other materials
  • Centrioles replicate to form 2 pairs

14
Cell Division
  • Splitting of one cell to form 2 cells
  • Divided into 2 parts
  • Mitosis
  • Cytokinesis

15
Cell Cycle
Cell Cycle
Cell Division
Interphase
Cytokinesis
Mitosis
G2
G1
S
16
Mitosis
  • Process during which a cells nucleus divides
    into two identical nuclei
  • It is divided into 4 phases
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase

17
Cell Cycle
Cell Cycle
Cell Division
Interphase
Cytokinesis
Mitosis
G2
G1
S
Prophase
Metaphase
Anaphase
Telophase
18
Prophase
  • Cromatin condenses
  • Proteins form microtubules which form a fibrous
    structure called the mitotic spindle
  • Spindle stretches out between opposite poles of
    the cell
  • Nuclear envelope and nucleolus
    break down
  • Centromere attaches to spindle fibers
  • Fibers move chromatids to center of
    cell

19
Metaphase
  • Chromosomes are pulled to center of cell
  • Chromosomes line up on an imaginary line called
    the metaphase plate
  • ALIGNMENT IS CRUCIAL TO ENSURE
    THAT EACH CELL GETS A
    COMPLETE SET OF CHROMOSOMES

20
Anaphase
  • Centromeres divide
  • Spindle fibers pull chromatids toward opposite
    poles
  • Ends when chromosomes are at opposite ends of the
    cell

21
Telophase
  • 2 daughter nuclei form
  • Nuclear envelopes form around each set of
    chromosomes
  • Nucleoli appear
  • Chromosomes uncoil to form chromatin
  • Mitotic spindle disassembles

22
Cytokinesis
  • Process in which the cells cytoplasm divides to
    make 2 daughter cells
  • Each daughter forms around 1 of the 2 nuclei
    produced during mitosis
  • Begins during telophase

23
Cytokinesis in Animal Cells
  • The cell membrane, at the center of the cell,
    folds inward to form a cleavage furrow
  • The cell continues to pinch in half at the furrow
    until the membrane meets and forms a division
    resulting in 2 cells with complete cell membranes

24
Cytokinesis in Plant Cells
  • In plant cells, a cell plate forms between the
    two new nuclei and then a cell wall forms around
    it
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