1. Chapter 9 Notes

2. Chapter 9 Notes Chromosomes Chromatin = DNA and proteins
-Most of the time DNA exists as long fibers of chromatin (so it fits inside the nucleus)

3. Chromosomes and Cell Division
Before mitosis chromosomes copy themselves.
Sister Chromatids: Two identical copies of a chromosome.
Centromere: The region where the two chromatids are joined.

4. Chapter 9 Notes 2 main phases in the cell cycle:
Interphase = 90% of time
Normal cell activities
Mitotic Phase = only when cell reproduces itself.

6. Three Periods of Interphase
S phase: The period when DNA is duplicated (copied). (S is for DNA synthesis.)
G1: G for Gap 1
The cell grows.
G2: Gap 2
The cell is preparing to divide.

7. Chapter 9 Notes Check yourself
1. What are sister chromatids joined by?
2. Chromatin is made up of _____ and _____
3. A cell spends 90% of it's time in which phase?
4. What are the 3 parts of interphase?

8. Chapter 9 notes - Mitosis
Mitosis = cell division to make normal body cells (skin cells, liver cells, muscle cells, etc.)

10. Steps of Mitosis 0. Interphase 1. Prophase 2. Metaphase 3. Anaphase
4. Telophase (& Cytokinesis)
Interphase is not part of Mitosis!!!

11. Helpful Hint
Create a neumonic to help you remember the order of the phases of mitosis.
Porsha met Ana for tea.
Prophase, Metaphase, Anaphase, Telophase

12. Mitosis Terms
Spindle – Football shaped framework of microtubules that guide the movement of chromosomes during mitosis.
Centrosomes – Two regions of cytoplasmic material where the spindle microtubules grow from.

13. Prophase 1. Chromosomes form consisting
of a pair of sister chromatids joined
by a centromere.
2. Nucleolus disappears and cell stops making ribosomes.
3. Mitotic spindles form.
4. Chromatids attach to the microtubles that make up the spindles
5. Spindles start tugging toward center of the cell.

14. Metaphase
1. Chromosomes gather in a plane across the middle of the cell.
2. Mitotic spindle is now fully formed.

15. Anaphase 1. Sister chromatids separate from their partners.
2. Daughter chromosomes move along the spindles toward the poles.

16. Telophase & Cytokinesis
1. Chromosomes reach the poles of the spindles.
2. Spindles disappear and two nuclear envelopes reform around each daughter set of chromosomes.
3. Chromosomes uncoil and the nucleolus reappears.

17. Cytokinesis Cytokinesis – cytoplasm divides into two daughter cells.

18. Check for Understanding
9. Describe what happens in anaphase.
10. Which phase is the arrow pointing to?