2. Review What is the cell cycle? What are the two stages of the cell cycle? Why do cells need to divide?

3. Chromosomes In cells DNA is tightly wound up into chromosomes Chromosomes are not visible, but become visible in mitosis

5. Humans have 23 pairs of chromosomes

6. Chromosome before DNA replication Chromosome after DNA replication

7. Chromatid – One half of a duplicated chromosome Centromere – Middle of a chromosome

8. Midlesson Review What is a chromosome? How many pairs of chromosomes do humans have? What is a centromere?

9. Mitosis 4 stages Prophase Metaphase Anaphase Telophase

10. Prophase 1 st stage Nuclear envelope breaks down Chromosomes become visible Spindle forms

11. Metaphase Chromosom es line up in middle Spindle attaches to each centromere

12. Anaphase Each sister chromatid is pulled apart

13. Telophase The two sets of chromosomes are now at separate ends of the cell Two nuclear envelopes form around the chromosomes

14. Cytokinesis –Not Mitosis-- After mitosis the cell splits in two Animals – cell pinches down the middle Plants – Cell plate forms down the middle

15. Review What are the 4 phases of mitosis? What happens in first stage of mitosis? What happens in the second stage of mitosis? What happens in the third stage of mitosis? What happens in the fourth stage of mitosis? What happens in cytokinesis?