1. Mitosis- Cell Division
Photo Credit: © CAMR/A.B. Dowsett/Science Photo Library/Photo Researchers, Inc.
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2. Why do cells divide by Mitosis?
Growth &Repair
Reproduction of single celled organisms
Maintenance constant environment
Amobea
Reproducing

3. Cells dividing by Mitosis…….
Skin
Identical to original cell
Same chromosome #
Identical chromosome makeup

4. The Cell Cycle
The sequence of growth and division of a cell.
95% of cell cycle in interphase
5% of cell cycle in mitosis

6. Events of the Cell Cycle
Mitosis
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.
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7. Interphase Growth Stage 1 (G1) – “Intermission”
During G1 phase
The cell increases in size
The cell synthesizes new proteins and organelles
Normal metabolic activity of the cell

8. Interphase Synthesis Stage (S) “Intermission” During the S phase,
metabolic activity of the cell continues
chromosomes are replicated
DNA synthesis takes place
Once a cell enters the S phase, it usually completes the rest of the cell cycle.

9. Interphase Growth Stage 2 (G2) – “Intermission”
The G2 Phase (Second Gap Phase)
metabolic activity of the cell, prepare for division
organelles and molecules required for cell division are produced
Once G2 is complete, the cell is ready to start the M phase—Mitosis

10. Interphase “Intermission” Normal metabolic activities Major state DNA=
chromatin

11. Where is DNA located?
1. Nucleus
2. Chromosomes
DNA I

12. Duplicated Chromosome (Late Interphase):X
Sister
Chromatids
Centromere

13. Stages of Mitotic Cell Division
Prophase
Metaphase
Anaphase
Telophase
“1st”
“middle”
“apart”
“far” or separate

14. Chromosomes (paired chromatids)
Mitosis
Section 10-2
Spindle forming
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.
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15. Prophase Nuclear membrane disappears
Doubled DNA = condensed now called “chromosomes”
Spindle fibers
Prophase

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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.
Spindle fibres form
Centromere
Chromosomes
(paired chromatids)
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Mitosis
Centriole
Spindle
Centriole
Metaphase
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19. Metaphase
Chromosomes line up mid- cell

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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
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22. Individual chromosomes
Mitosis
Individual chromosomes
Anaphase
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23. Anaphase Chromosomes move to opposite poles at Centrioles in animals
Spindle apparatus in plants

24. Spindle & spindle fibers: Pull apart the sister chromatids

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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
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27. Nuclear envelope reforming
Mitosis
Nuclear envelope reforming
Telophase
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28. Telophase
Cells divide
Cell plate or membranes form
Nucleus reappears

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Mitosis
Telophase
Telophase is the fourth and final phase of mitosis.
Chromosomes gather at opposite ends of the cell and lose their distinct shape.
A new nuclear envelope forms around each cluster of chromosomes
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Cytokinesis
Cytokinesis
Cytokinesis
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32. Cytokinesis:cell’s cytoplasm divides & splits apart

33. Returns to Interphase “Intermission” Normal metabolic activities
Major state
DNA=chromatin

34. Plant versus Animal Mitosis
Cell wall
cell plate in telophase
Spindles
Animal:
No cell wall
membrane cytokinesis
Centrioles

35. Animal Telophase
Interphase

36. Text Reference
2.5 pages 40-44
Q #1-5 page 44