1. CELL DIVISION OBJECTIVES: Describe the main events of the cell cycle.
Describe the structure of chromosomes.
Explain what happens during the four phases of mitosis.

2. Splitting up a cell
What do you think would happen if this cell suddenly split in half??
Cells must prepare
for cell division!

3. Getting the DNA ready
Chromosomes – structures in the nucleus that contain DNA and proteins.
Chromsomes are not visible except during cell division!
Before cell division, each
chromosome is copied!
chromatids
centromere

4. The Cell Cycle
Cell Cycle – the series of events that cells go through as they grow and divide.
2 major parts:
interphase
cell division

5. Interphase Interphase – period of time when the cell is not dividing.
Three phases:
G1 phase:
cell is growing and
doing its job.
S phase:
chromosomes are
copied.
G2 phase:
cell prepares for division.

6. Cell Division (M phase)
Cell division is divided into 2 parts:
mitosis – the division of the nucleus
cytokinesis – the division of the cytoplasm
Mitosis has 4 phases:
prophase
metaphase
anaphase
telophase

7. Mitosis phase 1: Prophase
First and longest phase of mitosis
Chromosomes become visible
Centrioles move to opposite sides of the cell and organize the spindle:
a fanlike structure that
separates the chromosomes.
Nuclear membrane breaks
down to open the nucleus.

8. Mitosis phase 2: metaphase
Lasts only a few minutes
Chromosomes line up in the center
Spindle attaches to the centromeres on the chromosomes

9. Mitosis phase 3: anaphase
Centromeres split, allowing the sister chromatids to separate
Spindle pulls the chromatids apart

10. Mitosis phase 4: telophase
Final phase of mitosis
Chromosomes unravel
Nuclear membranes form around each set of chromosomes to form two nuclei
Spindle breaks apart

11. cytokinesis
The cytoplasm pinches together until two new cells are formed.

12. Mitosis & Cytokinesis