cell cycle. why do cells divide? growth --by adding cells, not having them get bigger --cells are...

Cell Cycle

Why do cells divide?

• Growth--by adding cells, not having them get bigger--cells are not efficient for exchanging materials if they are too big--cells must have more surface area than volume

• Repair or Replacement• Reproduction

Three Steps in Cell Cycle

• Interphase- G1, S, and G2 – Cell grows and prepares for division– 90% of time is spent in this phase for a cell– Chromosomes copy themselves

• Mitosis- 4 steps of nuclear division

Prophase, Metaphase, Anaphase, Telophase

• Cytokinesis- division into two new cells

Mitosis

• Complex and delicate process

• 4 steps:– Prophase– Metaphase– Anaphase– Telophase

Prophase

• chromatin is developing into chromatids

• cell membrane is breaking down.

• Centrioles are moving toward poles and spindle fibers are forming

Metaphase

• nuclear membrane disappears.

• chromatids line up on the metaphase plate.

• spindle fibers are connected to the sister chromatids at the centromere.

Anaphase

• the sister chromatids separate by the pulling action of the centrioles on the spindle fibers.

Telophase

• The chromatids pulled to poles.

• The nuclear membrane is reforming

• A cell plate is developing between the two cells.

Cytokinesis• Cytokinesis and telophase take place at approximately the same time.

•Where mitosis is the division of the nucleus, cytokinesis is the division of the cytoplasm.

•Once the division of the cytoplasm is complete, two new cells have formed.

Answer the following questions

1. Is this an animal or a plant?

2. What phase is this slide in?

3. What helped you determine which phase this slide was in?

Answer the following questions

4. Is this an animal or a plant?

5. What phase is this slide in?

6. What helped you determine which phase this slide was in?

Answer the following questions

7. Is this an animal or a plant?

8. What phase is this slide in?

9. What helped you determine which phase this slide was in?

Answer the following questions

10. Is this an animal or a plant?

11. What phase is this slide in?

12. What helped you determine which phase this slide was in?

Answer the following questions

13. What phase is the cell the arrow is on in?

14. What phase is the cell to the left of that cell in?

15. Name the two differences between plant mitosis and animal mitosis.