1. Cell Cycle, Mitosis, and Meiosis

2. Why do cells divide?
Most cells go through a series of changes in order to maintain homeostasis. Cells need to reproduce (divide) when their surface area can no longer supply the much larger volume with nutrients and get rid of wastes.

3. Cell Division
The process by which a cell divides into two new daughter cells

4. Chromosomes
Made of DNA (carries the cell’s genetic information) and proteins
Every organism has a specific number of chromosomes
Humans have 46

5. Chromosomes Only visible during cell division
Each chromosome is copied before cell division
Each chromosome is made of two identical “sister” chromatids
Each pair of chromatids is attached by a centromere

6. The Cell Cycle
The series of events that cells go through as they grow and divide

7. The Cell Cycle
Interphase – the period of growth in between cell divisions
Three phases of interphase G1 S G2

8. Interphase – G1 phase Phase where cells do the most growing
Cells increase in size and make new proteins and organelles

9. Interphase – S phase Chromosomes are replicated (copied)
Synthesis (making) of DNA molecules occurs

10. Interphase – G2
Organelles and other molecules required for cell division are produced.
Once completed, the cell will enter mitosis

11. Mitosis The division of the cell nucleus
Divided into four phases (PMAT):
Prophase
Metaphase
Anaphase
Telophase

12. Prophase Chromosomes become visible Nuclear envelope breaks down
Centrioles separate
Spindles form

13. Metaphase
Chromosomes line up along the center of the cell

14. Anaphase Sister chromatids separate
Individual chromosomes are moved apart

15. Telophase Chromosomes gather at opposite ends of the cell
Two new nuclear envelopes form

16. Cytokinesis
The cytoplasm pinches in two – two new daughter cells are formed
In plants a cell plate divides the cytoplasm before the cell wall forms

17. Cancer Cells
1. Normal cells contain check points to regulate the cell cycle, & stop at appropriate check points.
2. Cancerous cells do not respond to check points and continue rapidly through the cell cycle. This results in masses of undefined cells called tumors.
3. Cancer cells do not mature; they become more immature.

18. Binary Fission
The asexual reproduction of a bacterial cell