1. Chromosomes & Cell Cycle
What the heck is a Chromosome anyway?

2. Chromosomes Chromosomes are tightly coiled rod like structures
They consists of DNA & proteins.

3. DNA itself is wound up into a thin fiber which is wrapped around proteins called “Histones”
The Histone & DNA structure forms a beadlike structure known as a “Nucleosome”

4. The Nucleosomes pack together to form a thick fiber which starts to coil.
These coils wind up even more and become “Supercoils”

5. The super coils are wound up to form a larger structure that is called a “Chomosome”
Only during cell division are these chromosomes ever visible.

6. What part of the chromosomes should I know?
Centromere – holds together the two chromatids
Sister Chromatids – genetic material from each parent

7. This is a duplicated copy
This is 1 chromosome

8. At one period of time scientists thought that cells were constantly dividing and replacing old and dead cells.
During the time they were not duplicating and just growing, scientists gave this term a name called:
“Interphase” – which means “resting phase”
Eventually scientists found that a lot happens between the resting phases. This is now what we call the “Cell Cycle”

9. CELL CYCLE
M phase

10. We start along this line and cover this section.
This section is known as the G1 phase
M phase
- This is where cells do most of their growing
G1 phase
- Cells synthesize new proteins and organelles.

11. After all the thngs in G1 are done, the cell then moves to the next phase in it’s life called the “S phase”
M phase
- Chromosomes are duplicated
G1 phase
- Key proteins used in replication are being made
S phase

12. After all the chromosomes have duplicated in the S phase, the cell then moves to the next phase in it’s life called the “G2 phase”
M phase
- Cell organelles and molecules required for cell division are being made.
G1 phase
S phase
G2 phase

13. Next comes the “M phase” which stands for Mitosis.
Mitosis is the actual cell division of one cell into two “daughter cells”
M phase
Mitosis has 4 parts in which we will cover each separately.
G1 phase
S phase
G2 phase

14. Mitosis has 4 steps to it:
Prophase
Metaphase
Anaphase
Telophase
I’ll show you how to draw a simple illustration for each step for your notes.
But first, let’s review 3 critical events during interphase just before the cell prepares to go into Mitosis.

15. Early Prophase The cell has divided all it’s DNA
The Nucleolus disappears
The Centrioles appear
It is now ready to divide.

16. PROPHASE Chromosomes form and then duplicate into “sister chromatids.”
The Nuclear envelope slowly disappears
The centrioles head to the poles
Spindle fibers start to appear

17. METAPHASE “In the military you form a line”
The sister chromatids line up in a straight line along the “Metaphase Plate”
2. Spindle fibers attach to the chromosomes near the middle called a Kinetochore

18. ANAPHASE
1. The spindle fibers pull apart the sister chromatids and pulls each chromosome toward its pole.
“Ana is a cheerleader – Cheerleaders do the splits”

19. TELOPHASE The Centrioles fade away.
The nuclear envelope starts to form
The chromosomes start to unwind to long strands
The cell starts to pinch in the center ready to split.

20. OK, we’re almost done, but the cell still has one more thing to go through before it gets out of the “m phase”
Cytokinesis
M phase

21. Cytokinesis Animal Cell
The Cell now has two separate nuclei
The Cell then pinches in the middle and splits in two
The 2 cells have the exact same DNA in each cells
The two cells are now called “Daughter Cells”
Movie Mitosis

22. Cytokinesis Plant Cell
Vesicles containing cell wall material forms a plate line
2. The vesicles connect to form a cell plate
3. The cell plate divides the daughter cells and becomes a cell wall.

23. Now could you identify the phase in a real cell?
ANAPHASE

24. METAPHASE

25. PROPHASE

26. CYTOKINESIS – (PLANT)

27. TELOPHASE

28. PROPHASE

29. METAPHASE
PROPHASE
ANAPHASE
Late ANAPHASE or EARLY TELOPHASE

30. 46 46 + 46 46 46 Mitosis → Daughter Cells →
The important thing to remember is that your two daughter cells
(the final product of Mitosis)
Will have the same number of chromosomes as the original cell did. 46
Mitosis → 46 46
Daughter Cells →

31. VOCABULARY ! Chromosome Histome Nucleosome Super coils Centromere
Chromatids
Interphase
Cell cycle
G1 phase
S phase
G2 phase
Mitosis
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Cell plate