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Mitosis. “The Life and Times of the Cell”. Objectives. List factors that influence when cells divide Understand & describe the ‘Cell Cycle’ Study the events of cell division (Mitosis) Compare Mitosis in plant & animal cells Cell Division Animation. Reading Assignment.

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“The Life and Times of the Cell”


List factors that influence when cells divide

Understand & describe the ‘Cell Cycle’

Study the events of cell division (Mitosis)

Compare Mitosis in plant & animal cells

Cell Division Animation

Reading assignment
Reading Assignment

  • Read Section 10-1, p.241-243 titled Cell Growth.

  • From the diagram indicating the Ratio of Surface area to Volume onp.243, sketch in your notes the smallest cell and the related statistics for Surface Area, Volume, and Surface Area to Volume Ratio and then sketch the largest cell with it’s related statistics.

  • Answer the 4 questions in 10-1 Section Assessment on p.243.

Cell cycle 4 phases
Cell Cycle – 4 Phases

  • Gap 1 (G1)

    • Typical cell growth & metabolism.

  • S Phase (S)

    • DNA Replication

  • Gap 2 (G2)

    • Centrioles Replicate

    • Protein synthesis

  • M Phase (M)

    • Mitosis phase / cell division occurs

Cell cycle
Cell Cycle

  • The G1, S and G2 stages of the Cell Cycle happen during INTERPHASE.

  • The M phase consists of: Prophase; Metaphase; Anaphase; Telophase; Cytokinesis

S phase dna replication
S Phase - DNA Replication

An enzyme called Helicase causes the hydrogen bonds that hold DNA together to break or ‘unzip’

Then DNA Polymerase allows free floating nucleotides to attach to the single strand of DNA

DNA is Replicated

Draw dna replication
Draw DNA Replication

  • Draw a DNA triplet with the base sequence ATG on the left side. Make the 5’ the top left.

Dna replication
DNA Replication

  • Separate the original DNA strands.

  • With different colors, show the attachment of free-floating nucleotides.

Dna replication1
DNA Replication

  • Where do the free-floating nucleotides come from?

  • Foods we eat!

  • How do the 2 strands compare?

  • They are exactly the same!

  • What happens if there is a mistake made during replication?

  • A mutation occurs!


DNA Replication..Who wants to try?

Replication Song

M phase mitosis 4 5 phases
M Phase – Mitosis (4/5 Phases)

  • 1. Interphase

    • G1, S, & G2 phases

  • 2. Prophase

    • Early & Late

  • 3. Metaphase

  • 4. Anaphase

  • 5. Telophase

    • Early & Late

  • Cytokenesis

Early prophase
Early Prophase

Replicated centrioles split and start moving to opposite sides of the cell forming ASTERS.

Nuclear envelop disappears

Replicated chromatin shortens, thickens and forms CHROMATID PAIRS

Late prophase
Late Prophase

Centrioles have reached opposite poles of the cell


Chromatid Pairs float throughout the cytoplasm.


Shortest stage of Mitosis

Chromatid pairs align at the equator of the spindle


Chromatid pairs split

Spindle fibers contract and the single CHROMOSOMES are pulled to opposite poles

Early telophase
Early Telophase

Often described as the opposite of prophase

Nuclear envelop reappears

The chromosomes unravel to become chromatin

Cleavage furrow begins to form

Late telophase
Late Telophase

Cleavage furrow completes it’s indentation.

“Mother” cell splits into 2 identical “Daughter” cells in a process called CYTOKINESIS

Summary of mitosis
Summary of Mitosis


Replicated chromatin condense into chromatid pair

Centrioles move to opposite poles

Nuclear envelope disappears

Spindle fibers start to form


Chromatid pairs line up at the equator


Chromatid pairs split

Chromosomes are pulled to opposite poles by the spindle fibers


Chromosomes de-condense into chromatin

Nuclear envelope reappears

Cytoplasm is divided into 2 cells



  • I don't watch television when I can talk about Cell Division!

One more phase gap 0 g0
One more Phase – GAP 0 (G0)

Some cells do not replicate their centrioles during Prophase.

They lose their ability to divide

They enter the Gap 0 stage

Neurons of the Spinal cord / Brain cells

Mitosis in plant vs animal cells the rivalry continues
Mitosis in Plant vs. Animal CellsThe Rivalry Continues

Plants have no centrioles but still form spindle fibers

Plant cells divide from the inside out

Cell Plate

“Messy Metaphase”

Importance of mitosis
Importance of Mitosis

Method of reproduction for all single celled organisms

Allows us to regenerate cells (tissue) repair cuts, bone breaks, etc

Growth – one cell to trillions

How long does the cell cycle last
How Long does the Cell Cycle Last?

  • Pick up a textbook and turn to page 249.

  • Read the section titled “Life Spans of Cells” and answer the 4 questions that follow.

Regulating the cell cycle
Regulating the Cell Cycle

  • Turn in your textbook to page 250. Read pages 250 to 252.

  • Answer the 5 questions that follow.

  • Terms: Contact Inhibition; Cyclins; Internal regulators; External regulators; Cancer;