1. Cell Cycle Interphase:
Period between the end of one mitosis and the beginning of the next.

2. Steps of Cell Cycle 1. G1 phase (gap 1): cell grows
2. S phase: DNA replicates (copy)
3. G2 phase: more growth
4. Mitosis: Cell divides.

3. Replication of DNA DNA’s Ability to make an exact copy of itself!
Occurs during S- phase of Cell Cycle, before mitosis.
Occurs at hundreds of places along DNA strand

5. Replication of DNA: 1. DNA Unzips:
Enzyme Breaks Hydrogen Bonds between nitrogenous base pairs
Creates 2 Complementary Strands (templates)
2. DNA Polymerase moves along original strands (templates)
Nucleotides come from the cytoplasm
DNA Polymerase attaches complimentary bases to both sides of the unzipped strands (Semi-Conservative).
3. Completed: 2 NEW identical strands of DNA are produced
DNA Polymerase “proofreads” the new strands

7. Chromosome Structure Two sister Chromatids Centromere:
Holds chromatids
together.
Chromosome

8. Chromosomes
Found in the nucleus of the cell

9. Chromosomes Contain DNA Number varies with organism: Humans: 46
Cats: 32
Dogs: 72
Karyotype: shows # of
Chromosome pairs

10. (pause… mitosis is next)

11. M-Phase: Cell Division
2 Steps:
1. Mitosis: Nucleus divides into 2 nuclei.
2. Cytokinesis: cytoplasm divides to form two new cells.
Takes 30 minutes to several hours.

12. Cell Division

13. Mitosis Animation
                                                                                                                                                                   

14. Stages of Mitosis

15. Interphase:
Animal cell:
Plant Cells:

16. 2nd: Prophase Mitosis begins (cell begins to divide)
Spindle fibers form between the ends (poles) of cell.

17. 3rd: Metaphase
Chromosomes line up at the center of the cell or equator
Spindle fibers attach to Chromatids, as they prepare to pull them apart

18. 4th: Anaphase
Chromatids (or pairs of chromosomes)) separate and begin to move to opposite ends of the cell

19. 5th: Telophase Two new nuclei form
Chromosomes appear as chromatin (threads rather than rods)
Mitosis ENDS

20. Cytokinesis
Cell membrane moves inward to create two daughter cells – each with its own nucleus with identical chromosomes