Cell division occurs through mitosis and cytokinesis to form two daughter cells. Mitosis involves four phases - prophase, metaphase, anaphase, and telophase - where chromosomes condense and separate. Cytokinesis then divides the cytoplasm. Most of a cell's life is spent in interphase, which prepares the cell for division. Cell division allows for growth, tissue repair, and asexual reproduction.

1. Cell DivisionCell Division

2. ChromosomesChromosomes
 Are made of DNAAre made of DNA
 Each chromosome consists of sisterEach chromosome consists of sister
chromatids attached at a centromerechromatids attached at a centromere

3. Cell CycleCell Cycle
 During the cell cycle, a cell grows,During the cell cycle, a cell grows,
prepares for division, and divides toprepares for division, and divides to
form 2 daughter cells, each of whichform 2 daughter cells, each of which
then begins the cycle again.then begins the cycle again.
 Interphase – time for growth andInterphase – time for growth and
regular cell activity.regular cell activity.
 Most of a cell’s life is spent inMost of a cell’s life is spent in
Interphase.Interphase.

4. InterphaseInterphase

5. Introduction to Cell DivisionIntroduction to Cell Division
A time when a cell performs its
usual functions, depending on the
location in the body.

6. MitosisMitosis
 The division of somatic or regularThe division of somatic or regular
cells.cells.
 Its divided into 4 phases.Its divided into 4 phases.
 Remember Interphase is NOT part ofRemember Interphase is NOT part of
Mitosis.Mitosis.

7. Introduction to MitosisIntroduction to Mitosis

8. ProphaseProphase
 First stage of MitosisFirst stage of Mitosis
 Chromatin condenses intoChromatin condenses into
chromosomeschromosomes
 Centrioles separate and a spindleCentrioles separate and a spindle
fiber begins to form.fiber begins to form.
 Nuclear membrane breaks downNuclear membrane breaks down

9. ProphaseProphase

10. MetaphaseMetaphase
 Second Phase of MitosisSecond Phase of Mitosis
 Chromosomes line up in the middleChromosomes line up in the middle
of the cell.of the cell.
 Each chromosome is connected to aEach chromosome is connected to a
spindle fiber.spindle fiber.

11. MetaphaseMetaphase

12. AnaphaseAnaphase
 Third Phase of MitosisThird Phase of Mitosis
 The sister chromatids separate intoThe sister chromatids separate into
individual chromosomes and moveindividual chromosomes and move
apart to opposite ends of the cell.apart to opposite ends of the cell.

13. AnaphaseAnaphase

14. TelophaseTelophase
 Fourth and Final Stage of MitosisFourth and Final Stage of Mitosis
 Chromosomes gather at oppositeChromosomes gather at opposite
ends of the cell and lose their distinctends of the cell and lose their distinct
shapesshapes
 Two new nuclear membranes haveTwo new nuclear membranes have
formed.formed.

15. TelophaseTelophase

16. CytokinesisCytokinesis
 The cytoplasm pinches in half.The cytoplasm pinches in half.
 Each daughter cell has an identicalEach daughter cell has an identical
set of duplicate chromosomesset of duplicate chromosomes

17. Regulating the CycleRegulating the Cycle
 A protein called cyclin helps regulateA protein called cyclin helps regulate
the cell cycle in eukaryotic cells.the cell cycle in eukaryotic cells.
 They respond to internal andThey respond to internal and
external events. These proteins areexternal events. These proteins are
regulators.regulators.

18. When Things Go WrongWhen Things Go Wrong
 Cancer cells do not respond to theCancer cells do not respond to the
signals that regulate the growth ofsignals that regulate the growth of
most cells.most cells.
 As a result, they form masses of cellsAs a result, they form masses of cells
called tumors that can damagecalled tumors that can damage
surrounding tissues.surrounding tissues.

19. The Cell Cycle in DepthThe Cell Cycle in Depth
 InterphaseInterphase
 Mitotic StageMitotic Stage
 CytokinesisCytokinesis
 ApoptosisApoptosis
 Cell Cycle and CancerCell Cycle and Cancer

20. INTERPHASEINTERPHASE
 3 STAGES3 STAGES
– GG11 stagestage
– S StageS Stage
– GG22 StageStage
– Some cells such as nerve and muscleSome cells such as nerve and muscle
cells typically do NOT complete the cellcells typically do NOT complete the cell
cycle and are said to have entered thecycle and are said to have entered the
GG00 stage.stage.
– For adult mammalian cells, interphaseFor adult mammalian cells, interphase
lasts ~20 hours (90% of cell cycle)lasts ~20 hours (90% of cell cycle)

21. INTERPHASE: GINTERPHASE: G11 stagestage
 Stage BEFORE DNA replicationStage BEFORE DNA replication
 Cell doubles its organelles andCell doubles its organelles and
accumulates materials for DNAaccumulates materials for DNA
synthesissynthesis
 G used to stand for “gap” but now itG used to stand for “gap” but now it
stands for “growth”stands for “growth”
– Protein synthesis is a part of theseProtein synthesis is a part of these
growth stagesgrowth stages

22. INTERPHASE: S stageINTERPHASE: S stage
 DNA synthesis/replication occursDNA synthesis/replication occurs
– Each chromosome is composed of oneEach chromosome is composed of one
chromatid (DNA double helix) andchromatid (DNA double helix) and
makes 2 sister chromatids (2 identicalmakes 2 sister chromatids (2 identical
DNA double helix molecules)DNA double helix molecules)

23. INTERPHASE: GINTERPHASE: G22 stagestage
 Stage from the completion of DNAStage from the completion of DNA
replication to the onset of mitosisreplication to the onset of mitosis
– The cell synthesizes protein that willThe cell synthesizes protein that will
assist cell division (i.e. protein found inassist cell division (i.e. protein found in
microtubules)microtubules)

24. M (Mitotic Stage)M (Mitotic Stage)
 The cell division stage that includesThe cell division stage that includes
mitosis (nuclear division) andmitosis (nuclear division) and
cytokinesis (division of thecytokinesis (division of the
cytoplasm)cytoplasm)

25. ProphaseProphase
 Nucleolus is disappearingNucleolus is disappearing
 Nuclear envelope is fragmentingNuclear envelope is fragmenting
 Spindle is forming betweenSpindle is forming between
centrosomescentrosomes
 Asters radiate from the centriolesAsters radiate from the centrioles
within the centrosomeswithin the centrosomes

26. PrometaphasePrometaphase
 Kinetochores of sister chromatidsKinetochores of sister chromatids
attach to kinetochore spindle fibersattach to kinetochore spindle fibers
extending from opposite polesextending from opposite poles
 Chromosomes move back and forthChromosomes move back and forth
until they are aligned at theuntil they are aligned at the
metaphase platemetaphase plate

27. MetaphaseMetaphase
 Spindle is fully formedSpindle is fully formed
 Duplicated chromosomes align atDuplicated chromosomes align at
metaphase platemetaphase plate
 Spindle consists of polar spindleSpindle consists of polar spindle
fibers that overlap at the metaphasefibers that overlap at the metaphase
plateplate
 Kinetochore spindle fibers that areKinetochore spindle fibers that are
attached to chromosomesattached to chromosomes

28. Anaphase
 Sister chromatids separate to
become daughter chromosomes that
move toward the poles
 Polar spindle fibers slide past one
another
 Kinetochore spindle fibers
disassemble
 Cytokinesis by furrowing begins

29. Telophase
 Nuclear envelopes re-form
 Chromosomes begin changing back
to chromatin
 Nucleoli reappear
 Spindle disappears

30. Plant CellsPlant Cells
 Lack centrioles and astersLack centrioles and asters
 Mitotic spindle still forms and goesMitotic spindle still forms and goes
through the same 5 mitotic phasesthrough the same 5 mitotic phases

31. CytokinesisCytokinesis
 In animal cells, it’s a furrowingIn animal cells, it’s a furrowing
process that divides the cytoplasmprocess that divides the cytoplasm
 In plant cells, the formation of a cellIn plant cells, the formation of a cell
plate from which the plasmaplate from which the plasma
membrane and cell wall aremembrane and cell wall are
completedcompleted

32. The Cell Cycle and CancerThe Cell Cycle and Cancer
 Cancer is due to the mutation ofCancer is due to the mutation of
genes that control the cell cyclegenes that control the cell cycle
 Cancer cells are…Cancer cells are…
– Are NondifferentiatedAre Nondifferentiated
– Divide repeatedlyDivide repeatedly
– Have abnormal nucleiHave abnormal nuclei
– Don’t require growth factorsDon’t require growth factors
– Not constrained by their neighborsNot constrained by their neighbors

33. The Cell Cycle and CancerThe Cell Cycle and Cancer
 After forming a tumor, cancer cellsAfter forming a tumor, cancer cells
metastasize and start new tumorsmetastasize and start new tumors
elsewhere in body.elsewhere in body.
 What you can do to try to preventWhat you can do to try to prevent
cancer…cancer…
– Avoid unnecessary radiationAvoid unnecessary radiation
– Avoid exposure to organic chemicalsAvoid exposure to organic chemicals
(ex: tobacco smoke)(ex: tobacco smoke)
– Have a diet rich in fruits and vegetablesHave a diet rich in fruits and vegetables

34. Prokaryotic Cell DivisionProkaryotic Cell Division
 Prokaryotic chromosome has a fewProkaryotic chromosome has a few
proteins and a single, long loop of DNAproteins and a single, long loop of DNA
 Binary fission- the chromosome attachesBinary fission- the chromosome attaches
to the inside of the plasma membrane andto the inside of the plasma membrane and
replicates.replicates.
 As cell elongates, the chromosomes areAs cell elongates, the chromosomes are
pulled apartpulled apart
 Inward growth of the plasma membraneInward growth of the plasma membrane
and formation of new cell wall materialand formation of new cell wall material
divide the cell in 2.divide the cell in 2.

35. Prokaryotic vs. Eukaryotic CellsProkaryotic vs. Eukaryotic Cells
 Binary fission (in prokaryotes) andBinary fission (in prokaryotes) and
mitosis (in cellular eukaryotic protistsmitosis (in cellular eukaryotic protists
and fungi) allow organisms toand fungi) allow organisms to
reproduce asexuallyreproduce asexually
 Mitosis in multicellular eukaryotes isMitosis in multicellular eukaryotes is
primarily for the purpose ofprimarily for the purpose of
development, growth, and repair ofdevelopment, growth, and repair of
tissues.tissues.