1. The Cell Cycle and Mitosis
Cell Division
The Cell Cycle and Mitosis

2. Why do cells divide?
Growth
Repair
Reproduction

3. Chromosomes
Carry genetic information from one generation of cells to the next
Not visible in cells except in cell division

4. Cell Division Process by which a cell divides into two daughter cells
Before division, the cell replicates all its DNA
Each daughter cell will get one complete set of genetic information

5. Cell Division- Prokaryotes
Binary fission: asexual cell division of prokaryotes that produces identical offspring
Three Steps:
DNA is copied
Cells begin to divide
Two identical cells

6. Binary Fission Bacterial cell dividing by binary fission
E. Coli dividing by binary fission

7. Cell Division- Eukaryotes
Nucleus first and then the Cytoplasm divides
There are two kinds:
Mitosis
Meiosis
Cell cycle: set of events making up the life of a cell; composed of interphase and cell division

8. The Cell Cycle

9. Interphase
The time between cell divisions where the cell spends most of its life
Cell is in a resting phase, performing cell functions
Composed of G1, S and G2 phases

10. Interphase

11. Interphase: G1, S, G2 G1 (Gap 1)- Cells grow to mature size
S (Synthesis)- DNA is copied
G2 (Gap 2)- cell organelles grow and prepare for division

12. Mitosis Division of nucleus
Daughter Cells wind up with the same # of chromosomes
There are 4 phases:
1. prophase 3. anaphase
2. metaphase 4. telophase

13. Prophase Chromosomes become visible
Centrioles separate and move to opposite sides of nucleus
Spindle fibers form

14. Prophase Nucleolus disappears
Nuclear Envelope breaks down and disappear
Prophase is the longest phase of cell division

15. Prophase

16. Metaphase
Chromosomes line up along the equatorial plate (middle of the cell)
Chromosomes connect to spindle fibers at centromere
Metaphase is the shortest phase

17. Metaphase

18. Anaphase Sister chromatids separate and move to opposite poles
When chromatids separate, they are considered individual chromosomes.

19. Anaphase

20. Telophase Nuclear envelope forms around each group of chromosomes
Chromosomes relax back into chromatin
Spindle fibers disassemble.
Cytokinesis begins

21. Telophase

22. Cytokinesis
The process by which the cytoplasm divides and one cell becomes two individual cells
Different in plants and animals
Animals- cell pinches inward to form a cleavage furrow
Plants- a cell plate forms between the two new cells forming a cell wall

23. Cytokinesis- Animal Cell

24. Cytokinesis- Plant Cell

25. Cytokinesis- Plant vs. Animal