1. Cell Growth and Division

2. Stress on DNA Where is DNA held in eukaryotic cells?
Does the amount of DNA increase as the cell increases? Why is this stressful?
As the cell increases in size, which increases faster: the volume or the surface area?

3. How do you calculate surface area: volume ratios?
Surface area of a cube: length x width x 6 (6 faces on a cube)
Volume of a cube: length x width x height
Ratio can be represented with a colon or as a fraction, such as 1:2 or 1/2

4. 1x1x 6 = surface area of 6 square mm
1x1x1 = volume of 1 cubic mm
2x2x6 = surface area of 24 square mm
2X2X2 = volume of 8 cubic mm
4x4x6 = surface area of 96 square cm
4X4X4 = volume of 64 cubic mm

5. So what are their surface area to volume ratios?
First cell 6:1
Second cell 24:8, which reduces to 3:1
Third cell 96:64, which reduces to 1.5 :1
…so there is less and less surface area available to support the volume of the cell

6. The Cell Cycle

7. The Cell Cycle an overview
What must happen to a cell before it can divide?
Copy DNA and grow in size (interphase)
Nucleus will divide (Mitosis)
Cytoplasm divides (Cytokinesis) and the two daughter cells enter Interphase

8. The Importance of Mitosis
Many unicellular organisms reproduce this way (asexual reproduction)
Multicellular organisms use mitotic cell division for numerous reasons
Growth
Development
Repair
NOT FOR SEXUAL REPRODUCTION (that is meiosis)

9. How does the DNA copy itself
DNA replication
Chromosomes copied
Sister chromatids remain connected by a centromere
Eventually, they will be separated into the two daughter cells

10. Interphase First and longest stage of cell cycle Subdivided G1: grow
S: synthesis of DNA
G2: grow organelles used in mitosis

11. Mitosis Prophase, Metaphase, Anaphase, Telophase
During Mitosis, the nucleus will be divided into two
Prophase
Metaphase
Anaphase
Telophase

12. Prophase (preparation)
Chromosomes
Centrioles
Spindle fibers

13. Metaphase (middle)
Chromosomes
Spindles

14. Anaphase (apart)
Centromeres split
Sister chromatids separate to poles

15. Telophase (two) Chromosomes uncoil Nuclear envelope reforms
Spindle breaks apart
Mitosis is now complete, but the rest of the cell still needs to divide

16. Cytokinesis the end of the M phase
Two nuclei
Cytokinesis is the division of the cytoplasm, and usually occurs simultaneously with telophase
cleavage furrow vs. cell plate

17. Cytokinesis
Cleavage furrow in animal cells
Cell plate in
plant cells

19. Test Yourself Mitosis and Meiosis
A. You will be shown images of cells in various stages of the cell cycle. Identify each stage.
B. We will go over the answers.
C. You will identify the stages individually and turn your papers in.

20. Test Yourself –Part A A B C D E F G H

21. We’ll go over the answers now
Everyone Done?
We’ll go over the answers now

22. Test Yourself-Part B
A. Telophase B C D E F G H

23. Test Yourself
A. Telophase
B Metaphase C D E F G H

24. Test Yourself
A. Telophase
B Metaphase
C Anaphase D E F G H

25. Test Yourself
A. Telophase
B Metaphase
C Anaphase
D Prophase E F G H

26. Test Yourself A. Telophase B Metaphase C Anaphase D Prophase
E Anaphase F G H

27. Test Yourself A. Telophase B Metaphase C Anaphase D Prophase
E Anaphase
F Interphase G H

28. Test Yourself A. Telophase B Metaphase C Anaphase D Prophase
E Anaphase
F Interphase
G Metaphase H

29. Test Yourself A. Telophase B Metaphase C Anaphase D Prophase
E Anaphase
F Interphase
G Metaphase
H Prophase

30. One last practice—can you find each stage?

31. Any Questions? Quiz Time! Number your paper 1-5
Identify the stage of the cell
cycle shown in each image

32. Question 1 Identify the stage shown below
Metaphase

33. Question 2 Identify the stage shown below
Prophase

34. Question 3 Identify the stage shown below
Telophase

35. Question 4 Identify the stage shown below
Anaphase

36. Question 5 Put these words in chronological order
Anaphase
Cytokinesis
Interphase
Metaphase
Prophase
Telophase
Interphase, Prophase, Metaphase, Anaphase, Telophase, Cytokinesis

37. Parson, LRCHS, 2007