Cell Division

1
Cell Division

• Mitosis
• Cytokinesis

2
What is Mitosis?

• Mitosis is the division of the cell nucleus.
• There are 4 main events or phases make up
  mitosis
• Prophase
• Metaphase
• Anaphase
• Telophase

3
Prophase

• Replicated chromatin from interphase begins to
  shorten , thicken , and coil up to form Chromatid
  Pairs.
• Nucleolus nuclear envelope disappears.
• Centrioles split and move to opposite sides of
  the cell (moves to the poles). Protein fibers
  begin to radiate from each. These structures are
  called Asters.
• When asters reach opposite sides of cell they
  form a Spindle.

4
Prophase

• Note Plant Cells do not have centrioles or
  asters but somehow these spindles still form?

5
Metaphase

• Shortest stage of mitosis.
• Chromatid pairs align at the equator of the
  spindle.

6
Anaphase
7
Anaphase

• Centromere splits and chromatid pairs separate.
• Spindle fibers begin to contract and drag the
  Chromosomes to opposite sides of the cell.

8
Telophase
9
Telophase

• Final stage of mitosis , chromosomes reach the
  poles and begin to uncoil to form chromatin.
• Spindle fibers disappear , nuclear envelope
  nucleolus begin to re-appear.
• In early telophase the cell membrane begins to
  indent at the equator to form a Cleavage Furrow
  (start of actual cytoplasm division called
  Cytokinesis).
• In late telophase cleavage furrows have indented
  further.
• MITOSIS IS NOW OVER !!

10
What is Cytokinesis

• Refers to the division of the cytoplasm to
  produce 2 genetically identical daughter cells.
• Animal Plant cells achieve cytokinesis
  differently.

11
Animal Cell

• Animal cell divides from the outside in by
  forming these cleavage furrows. The cleavage
  furrows eventually pinches off the middle.

12
Plant Cell Cytokinesis

• Plant cells divide from inside out through the
  formation of a Cell Plate.

13
Cell Division Questions
14
Assignment

• On page 249 read the box under
• analyzing data entitled Life Spans of
• Human Cells.
• 1. Re-copy the chart.
• 2. Answer using complete sentences
• the questions posed under each of
• the 4 sections within the box.