B I O LO GY 1 2

THE CELL CYCLE: A CLOSER LOOK!

FUNNY?

REVIEW (FROM LAST CLASS):

WHICH STAGE IS LONGEST?

INTERPHASE

• Aka the resting phase (but not really…)• Essentially, the cell is in between divisions and is

carrying out maintenance activities of the cell• Made up of 3 sub-phases:

1. G1 phase2. S phase3. G2 phase

INTERPHASE: G1 PHASE

• 1st growth phase • Cell mature by making more cytoplasm &

organelles• Cell carries on its normal metabolic activities,

such as synthesising proteins

Two identical copies of DNA

Original DNA

INTERPHASE: S PHASE• Synthesis stage• DNA is copied or replicated

INTERPHASE: G2 PHASE

• 2nd Growth Stage• Occurs after DNA has been copied• All cell structures needed for division are

completed (e.g. centrioles)• Both organelles & proteins continue to be

synthesized

MITOSIS

• Aka karyokinesis• Division of the nucleus• Only occurs in eukaryotes

• Made up of 4 phases:1. Prophase2. Metaphase3. Anaphase4. Telophase

MITOSIS: PROPHASE

• Early prophase:• Centrioles: make spindle fibres and move towards

opposite plates• Chromosomes shorten and thicken (now visible under a

microscope)

• Late prophase:• Centrioles reach poles• Nuclear membrane (envelope) & nucleolus start to

disappear

MITOSIS: METAPHASE

• Spindle fibres attach to centromeres• Sister chromatids (doubled chromosomes) line up

at equator (middle of cell)• Guided by spindle fibers

MITOSIS: ANAPHASE

• Centromeres divide in two• Spindle fibers contract

and pull sister chromatids towards opposite ends of cell (pole)• Each pole (future

daughter cells) will have an identical set of chromosomes

MITOSIS: TELOPHASE

• Sister chromatids at opposite poles• Spindle disassembles• Nuclear membrane forms

around each set of sister chromatids• Nucleolus reappears• Chromosomes loss their

distinct outlines reappear as chromatin

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IN PICTURES:•Prophase•Metaphase•Anaphase•Telophase

CYTOKINESIS:

• Means division of the cytoplasm• Division of cell into two, identical halves called

daughter cells• Would this happen the same way in plants and

animal cells? Why or why not?• In plant cells, cell plate forms at the equator to divide cell• In animal cells, cleavage furrow forms to split cell

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CYTOKINESIS

Cleavage furrow in animal cell

Cell plate in animal cell

HELPFUL HINT?

• Interphase• Prophase• Metaphase• Anaphase• Telophase• Cytokinesis

IPMATC

Amimation:

• http://www.youtube.com/watch?v=AhgRhXl7w_g&feature=fvsr

TO DO:

• Mitosis colouring sheet• Labelling sheet• Nelson Bio 11 Book• #1 to 9