1. Cell Cycle and Mitosis

2. Focus Questions
Identify the stages of mitosis and explain what is happening in each step
Why is cell division necessary for cells?

3. Cell Division
Cell division is when one cell splits or divides into 2 (or more) new cells.

4. Purposes of cell division
Reproduction in single-celled organisms (asexual reproduction)
Growth in multi-cellular organisms
Wound repair
Distributes identical sets of chromosomes to new cells

5. DNA DNA is stored in long strands called Chromosomes
Chromosomes are made up of DNA

6. Chromosomes
When two identical chromatids are joined together, they are called sister chromatids.
Sister chromatids stick together at a special part of the chromosome called the centromere

7. The Cell Cycle
The cell cycle is all of the stages in the life of a cell; the life cycle of a cell.
The cell cycle is divided into two major phases: Interphase and Cell Division or M Phase
Interphase: The cell is preparing to divide
G1 = the cell grows (growth phase)
S phase = the DNA is replicated or copied
G2 = the cell prepares to divide

8. The Cell Cycle continued….
Cell Division or M Phase:
Mitosis – division of the nucleus and DNA
Cytokinesis – division of the cytoplasm of the cell

9. Mitosis Mitosis is divided into 4 phases Prophase Metaphase Anaphase
Telophase
PMAT

10. Prophase Chromosomes condense
Centrioles (in animal cells) take position on opposite sides of the nucleus
Nuclear envelope disappears
Spindle fibers form and attach to chromosomes
** plant cells do not contain centrioles

11. Metaphase Chromosomes line up down the center of the cell
Aster form at the poles of the cell

12. Anaphase Sister chromatids split
Chromatids migrate towards the cell poles

13. Telophase Final phase of mitosis Nuclear envelopes reform
Chromosomes uncoil
Cleavage furrow in animal cells
Cell plate in plant cells

14. Cytokinesis
Cytoplasm divides equally among the daughter cells

15. How do cells know when to divide?
Signals from the nucleus tell the cell when to divide
Age or size of the cell can trigger division
Cells stop dividing when they touch other cells = Density Dependent inhibition
Cancer is when cells continue to divide out of control