1. Agenda for 12/1- Cell Cycle, Division (Mitosis)
Bellwork
New Information: Cell Cycle, Mitosis
Lab/Activity: Identifying Stages of the Cell Cycle- virtual lab
Link to quizlet:
Honors-
CP-

2. Bellwork
Domestic horses have 64 chromosomes. How many chromosomes should be in an egg cell of a female horse? A. 16 B. 32 C. 64 D. 128

3. Cell Cycle and Cell Division (Mitosis)
What is mitosis? Why is it important?

4. Cell Division 3 reasons for mitotic cell division (mitosis):
Growth
Repair
Replacement
Parent cell divides into two identical daughter cells

5. Cell Division
Cells divide to make new cells- DNA is replicated so each daughter cell gets an exact copy.
DNA condenses into chromosomes during mitosis. 5

6. Cell Division Humans have 46 chromosomes, 23 from each parent.
Haploid cells: only one of each chromosome (n)
Diploid cells: two of each chromosome (2n)

7. Cell Cycle (click for video clip)
G1 phase
M phase
S phase
G2 phase

8. Interphase- longest G1 Phase Cell growth S Phase DNA replication
preparation for mitosis
M Phase
mitosis and cytokinesis
Allium G1
M phase S G2

9. Interphase Nucleus and nuclear envelope are visible.
One or more nucleoli are visible.
The rest of the nucleus is filled with chromatin.

10. Figure 10-5 Prophase Interphase Cytokinesis Metaphase Telophase
Anaphase

11. Prophase pro- = first; first stage of mitosis
Nuclear envelope breaks down
Chromatin condenses into chromosomes
Centrioles move to opposite poles of the cell
Spindle fibers attach to chromosomes at the centromere.
(plant cells have microtubule organizing centers instead of centrioles)

12. Metaphase Chromosome line up in the Middle of the cell
Chromosome centromeres attach to the spindle at the poles of the cell

13. Anaphase
Chromosome centromeres separate and sister chromatids move Apart to the opposite ends of the cell

14. Telophase Chromosomes precipitate back into strands of DNA (chromatin)
A new nuclear membrane begins to form around each of the two new clumps of DNA

15. Cytokinesis Same time as Telophase Animal Cells:
(“cell splitting”)
Same time as Telophase
Animal Cells:
cytoplasm splits as the cell membrane draws inward (cleavage furrow) and splits the cell in two
Plant Cells:
cytoplasm splits as a cell plate forms between the two new nuclei, then a new cell membrane

16. Cell Cycle and Mitosis I P M A T C I Protect Mothers And Their
Children
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

17. Cell Cycle and Mitosis Virtual Lab
Go to
Make a table like the one you’ll see before the activity begins.
Answer the following questions:
Which phase of the cell cycle is longest? How do you know? Which is shortest, and how do you know?

18. Lab Objectives
To list the phases of the cell cycle in the order in which they occur.
To list the phases of the M-phase of the cell cycle (Mitosis) and explain what happens during each.
To illustrate/draw what happens during each phase of Mitosis.
To identify the role of cell structures during cell division (centrioles, chromatin, chromosomes, nucleus).
To learn the importance of cell division for organisms (asexual reproduction, growth, repair).

19. Mitosis in Allium Root
Interphase
Prophase
Metaphase

20. Mitosis in Allium Root
Anaphase
Telophase

22. Bellwork What are the 4 phases of the cell cycle?
What are the 4 phases of mitosis?
What is the significance of the phrase “I Protect Mothers And Their Children?”
What phases are shown below?

23. Binary Fission
Prokaryotes (bacteria) reproduce by a type of cell division called binary fission.
In binary fission the bacterial chromosome replicates and the two daughter chromosomes actively move apart.

24. G1 phase
M phase
S phase
G2 phase

25. The Cell Cycle Control System
The events of the cell cycle are directed by a cell cycle control system, similar to a clock.
Figure 12.14
Control system
G2 checkpoint
M checkpoint
G1 checkpoint G1 S G2 M

26. The Cell Cycle Control System
There are specific checkpoints where the cell cycle stops until a go-ahead signal is received.
G1 checkpoint G1 G0
(a) If a cell receives a go-ahead signal at the G1 checkpoint, the cell continues on in the cell cycle.
(b) If a cell does not receive a go-ahead signal at the G1checkpoint, the cell exits the cell cycle and goes into G0, a non-dividing state.
Figure A, B

27. Control of Cell Division
In density-dependent inhibition crowded cells stop dividing.
Most animal cells exhibit anchorage dependence in which they must be attached to a substratum to divide.
Cells anchor to dish surface and
divide (anchorage dependence).
When cells have formed a complete single layer, they stop dividing (density-dependent inhibition).
If some cells are scraped away, the remaining cells divide to fill the gap and then stop (density-dependent inhibition).
Normal mammalian cells. The availability of nutrients, growth factors, and a substratum for attachment limits cell density to a single layer.
(a)
25 µm
Figure A

28. Control of Cell Division
Cancer cells: no density-dependent inhibition or anchorage dependence.
Do not respond normally to the body’s control mechanisms and form tumors.
Loss of the cell cycle controls.
25 µm
Cancer cells do not exhibit anchorage dependence or density-dependent inhibition.
Cancer cells. Cancer cells usually continue to divide well beyond a single layer, forming a clump of overlapping cells.
(b)
Figure B

29. Control of Cell Division
Malignant tumors invade surrounding tissues and can metastasize, exporting cancer cells to other parts of the body where they may form secondary tumors.

30. Eukaryotic Cell Division
Mitosis- normal cell division
Parent cell divides into two identical daughter cells (diploid = 2n)
n = number of types of chromosomes
Meiosis- cell division resulting in sex cells (gametes)
Parent cell divides into 4 daughter cells, each with half the number of chromosomes (haploid = 1n)

31. Mitosis
2 diploid daughter cells formed, just like parent cell (two of each chromosome)
Preceded by interphase (G1, S, G2 phase)
Mitosis:
Prophase
Metaphase
Anaphase
Telophase

32. Figure 10-5 Prophase Interphase Cytokinesis Metaphase Telophase
Anaphase

33. Meiosis occurs in somatic cells to produce sex cells
4 haploid daughter cells formed (only one of each chromosome)
Preceded by interphase and DNA replication
Meiosis I
Meiosis II

34. Meiosis
Meiosis I- like mitosis but only one copy of each homologous chromosome goes to each new cell; two new cells formed
Prophase I
Metaphase I- homologous chromosomes line up on equator
Anaphase I- homologous chromosomes separate
Telophase I- two new cells, each with half the genetic material (one copy of each chromosome)
Meiosis II- the two cells formed in Meiosis I divide again
Basically like Mitosis

35. Mitosis vs. Meiosis Animation Mitosis- 2 diploid cells produced
Meiosis- 4 haploid cells produced
Why?
Mitosis- 2 exact copies of parent cell- to replace cells
Meiosis- 4 haploid cells, only half the genetic material, so
gametes can combine to produce a new organism