Mitosis: Cell Division

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MitosisCell Division
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Why do cells divide?

• Growth
• Repair
• Replace dead cells

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What cells divide often?

• Skin
• Stomach lining
• Red Blood cells
• Embryo
• Plant roots
• Hair
• Nails

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What cells rarely/never divide?

• Nervous System
• Liver

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Why do we age?

• Eventually cells stop being replaced
• Apoptosis
• Cell death
• We die because out cells die.
• William R. Clark

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C Terms

• Chromosomes
• Long threads of genetic material
• Found in nucleus
• Chromatid
• One side of a duplicated chromosome

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C Terms

• Centromere
• Structures that hold sister chromatids together
• NOTE
• 2 sister chromatids 1 duplicated chromosome

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C Terms

• Chromatin
• DNA tnagled around a histone (a protein)
• Condensed chromatin chromosome

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Huh?
C. Duplicated chromosome
A. DNA
B. Chromatin
histone
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C Terms

• Centrioles
• Small protein bodies
• In cytoplasm
• Animal cells only

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Cell Division in a Nutshell

• Before
• Chromosome duplicates 2 sister chromatids
• During
• Sister chromatids separate
• After
• 2 daughter cells
• Genetically identical

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Cell Cycle

• Mitotic phase
• 10
• Interphase
• 90

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Interphase

• Made up of three phases
• G1, S, G2
• What happens?
• Things necessary to divide

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Interphase

• G1 Phase
• Cell Growth
• 8-10 hours
• S Phase
• DNA replication
• Chromosome replication
• 6-8 hours
• G2 Phase
• More Cell Growth
• Centriole replication
• 4-6 hours

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Mitotic Phase

• Mitosis
• Division of nucleus (chromosomes)
• Occurs after interphase
• Cytokinesis
• Division of cytoplasm
• Creates 2 daughter cells
• Occurs at the end of mitosis

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Mitosis Phases

• Interphase
• Prophase
• Prometaphase
• Metaphase
• Anaphase
• Telophase

IPPMAT
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Task

• Draw a diagram of mitosis
• Label 6 phases give each a short description

IPPMAT
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Interphase

• Resting Phase
• Cell NOT dividing
• Precedes mitosis
• Prepares cell for division
• How?

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Early Prophase

• Centrioles
• Make spindle fibres
• Move towards opposite plates
• Chromosomes now visible

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Late Prophase

• Centrioles reach poles
• Nuclear membrane (envelope) nucleolus start to
  disappear

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Metaphase

• Spindle fibres attach to centromeres
• Duplicate chromosomes line up at equator
• Guided by spindle fibers

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Anaphase

• Spindle fibers retract
• Pull sister chromatids apart
• Towards opposite polls

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Telophase

• Chromatin reappears
• Nuclear membrane nucleolus reappear
• Cytokinesis occurs
• Result
• Two daughter cells

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What phases do you see?
B
A
D
C
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Cytokinesis

• Why would it occur differently in animal and
  plant cells?
• Plant cells have a rigid cell wall!

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Cytokinesis

• Animal Cells

• Cell membrane pinches inward
• Creates cleavagefurrow
• Think
• Pull a string around a balloon

• Plant Cells

• Cell Plate forms between two new nuclei
• Becomes cell wall

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Cytokinesis
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Cytokinesis
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Plant vs. Animal Another Difference?

• Centrioles not present in plant cells
• What makes spindle fibers in plant cells?
• Form from cytoskeleton

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Concept Map