Phases of Cell Division (Mitosis)

G1 Interphase

• Cell is metabolically active

• Organelles duplicate 

• Centrosome replication begins 

G2 Interphase

• Cell growth continues

• Enzymes & other proteins are synthesized

• Centrosome replication is completed

• Begins to reorganize its contents in preparation for mitosis

S phase

• The cell synthesizes a complete copy of DNA in the nucleus

• Duplicates a microtubule organizing structure called the centrosome

→ centrosomes help to separate DNA during the M (mitotic phase)

Prophase

• Chromatin condenses into chromosomes 

• Nuclear membrane breaks down and disappears 

• Centrosomes move to opposite poles 

•  Mitotic spindles (microtubules) begin to form

→ Spindles connect to each chromosome’s centromere via the kinectochore (a complex of proteins on the centromere that act as an attachment point)

Metaphase 

Centromeres of chromosomes line up along the middle of the cell & attach to the spindle fibers from opposite cell poles

Anaphase

• Centromeres of chromosomes break apart 

• Spindle fibers pull sister chromatids toward opposite poles of the cell 

Telophase

• The mitotic spindles dissolve 

• Chromosomes regain their chromatin appearance 

• A new nuclear membrane forms 

• A cleavage furrow forms & deepens

Cytokinesis

Parent cell splits, dividing the cytoplasm and nuclei into 2 identical cells