1. Chapter 9: The Cell Cycle
Section 1

2. Chromosomes are the structures that contain genetic material that is passed on from generation to generations of cells.

3. Chromatin is the relaxed form of DNA in the cells nucleus.

4. Recap! You guys read last week about cell size and the limitations to this. Can anyone tell me what they remember from the reading?

5. Once a cell reaches its size limit it will either die or divide.
*Cellular division is the way a cell reproduce as well

6. Cell reproduction by a cycle of growing and dividing is called the Cell cycle.

7. Each time a cell goes through one complete cycle, it becomes two individual cells. When, repeated over and over again! millions of new cells are made!

8. There are three main stages of the cell cycle.
Interphase, the stage in which the cell grows, carries out cellular function, and replicates, or makes copies of its Genetic material (DNA) in preparation for the next stage of the cell cycle.

9. Interphase is subdivided into three groups; 𝐺 1 , 𝑆 𝑎𝑛𝑑 𝐺 2

10. During 𝐺 1 , the cell grows and carries out normal cellular function in preparation to replicate DNA (genetic material).

11. During the S phase, the cell copies its DNA in preparation for cell division.

12. The 𝐺 2 stage is the period when the cell prepares for the division of its nucleus. The cell also takes inventory at this time and makes sure it is ready to continue with Mitosis. If it passes this check point it will go on.

13. Mitosis, the stage of the cell cycle during which the cell’s nucleus and Nuclear Material divide and separate to opposite ends of the cell. * Mitosis itself is subdivides into four stages.

14. At the end of mitosis, Cytokinesis begins.
Cytokinesis is the method by which a cell’s cytoplasm divides, creating two identical cell.

15. How long does this process take?
Time of the cell cycle depends on the type of cell. Some Eukaryotic cells take up to 8 minutes, while other cells might take up to a year.
For most normal cells, it takes about hours for this process to be carried out.

16. Mitosis and Cytokinesis
Section 2

17. RECAP!
Yesterday we talked about the cell cycle. We went over how cells go through interphase ( 𝐺 1 , 𝑆, 𝐺 2 ), Mitosis, and Cytokinesis.
During interphase, the cell is growing, replicating the DNA within the nucleus, and Preparing to split the nucleus to move on to the other phases.

18. During Mitosis, the cell’s replicated DNA and the cell prepares to separate into two cells.
During Cytokinesis, the cell’s cytoplasm divides creating two identical daughter cells.

19. Mitosis
The key activity for mitosis is the accuracy in the separation of the cell’s replicated DNA.
This allows the genetic information to pass on to the new cells, resulting in two identical Daughter cells.

20. Each half of the X is called a sister chromatid.
Each structure contains identical copies of DNA.
The structure at the middle of the chromosome is called a centromere.

21. In Multicellular organisms, such as ourselves, Mitosis increases the number of cells as a young organism develops into its adult size.

22. Organisms also use mitosis to replace damaged cells.
Think back to the last time you scraped your knee or got a cut.
Your body’s healing process involves creating new skin cells from your already existing cells.
Under your scab, your existing skin cells will divide my mitosis and cytokinesis, creating new skin that will fill the gab caused by your cut.

23. Reflect back to yesterday
Reflect back to yesterday! Mitosis occurs after interphase has completed.

24. Stages of Mitosis

25. Mitosis is Divided into Four Stages
*A good way to remember these Stages in order is to remember P-MAT
Prophase Metaphase Anaphase Telophase

26. Prophase This is the First and longest stage of mitosis.
In this stage the cells Chromatin tightens into chromosomes (shaped like an X).

27. As prophase continues
The nucleus disappears
Microtubule structures called spindle fibers form in the cytoplasm.
Centrioles migrate to the ends of the cell.

28. Coming out of the centrioles are a type of fiber called aster
Coming out of the centrioles are a type of fiber called aster. (creates the star like appearance)
The whole entire structure (spindle fibers, centrioles , asters) is called The Spindle apparatus.
This structure is important for the moving and organizing of the chromosomes for Division.

29. At the end of prophase:
The nuclear envelope disappears.
The spindle fibers attach to the sister chromatids of each chromosome on both sides of the cell.

30. Metaphase
During metaphase, the sister chromatids are pulled by motor proteins along the spindle apparatus toward the center of the cell and they line up in the middle.
This is one of the shortest stage of mitosis but one of the most important for it insures that the chromosomes have been copied accurately.

31. Anaphase During anaphase, the chromosomes are pulled apart
The microtubules of the spindle apparatus become shorter, therefore pulling the sister chromatids apart. Separating them into identical chromosomes.
At the end of anaphase, the chromosomes will be completely pulled to the opposite ends of the cell.

32. Telophase Chromosomes reach the poles (ends) of the cell.
Nuclear envelope re- forms.
Nucleus reappears
Chromosomes relax back into chromatin.

33. Cytokinesis
Recall from yesterday that this occurs at the end of mitosis.

34. Cytokinesis In a plant cell: In an animal cell:
Cell plate forms dividing daughter cells
In an animal cell:
Cleavage furrow forms an equator of cell and pinches inward until cell divides into two.

36. What is a centromere?
What is half of a chromosome called?
Where are the chromosomes located during Metaphase?
What is the acronym for mitosis?
After what stage of the cell cycle does Mitosis occur?