CELL CYCLE

1. CELL CYCLE • Over time, many of the cells die and need to be replaced. • The process by which a cell reproduces to create two identical copies is known as mitosis. • Cells formed by mitosis are known as daughter cells. • The cell division process occurs as four different stages, known collectively as the 'cell cycle'. • Many of the abnormal traits of cancer cells are due to defects in genes that control cell division.

3. Cell Cycle • The cell cycle consists of four stages G1, S, G2, and M. • G1 and G2 are 'gap' phases in which the cell grows and prepares to divide. • S in the synthesis phase in which the chromatin (DNA) is copied (replicated). • M is the mitotic phase in which the cell physically divides into two daughter cells. • Most cells are NOT actively dividing. These cells are in a resting state (G).

5. Mitosis is a process where cells are produced for growth and/or replacing damaged or old cells • Mitosis in normal cells produces two cells with identical genetic content. • Mitosis has four sub-phases:

6. PROPHASE • Chromosomes condense, the nuclear membrane breaks down, and spindle fibers form

7. METAPHASE • The replicated chromosomes line up in the middle of the cell

8. ANAPHASE • Chromosomes separate and the cell becomes elongated, with distinct ends (poles)

9. TELOPHASE • Nuclear envelopes re-form at the two poles and new cell membranes begin to form to create two independent cells

10. CYTOKINESISthe division of the cytoplasm to make two complete daughtercells • ANIMAL CELLS • Cell membrane pinches apart into two equal parts with one nucleus in each daughter cell • PLANT CELLS • Cell plate forms between two nuclei • Cell plate develops into a cell wall

11. Animations http://www.johnkyrk.com/mitosis.html http://www.hybridmedicalanimation.com/anim_mitosis.html

12. CYTOKINESIS

15. METAPHASE

18. PROPHASE

20. ANAPHASE

22. Quiz • http://www.biologycorner.com/flash/mitosis.html