1. Chapter 12 – The Cell Cycle
AP Biology

2. In 1855 Rudolf Virchow stated
“where a cell exists, there must have been a preexisting cell, just as animal arises from animal and plant arises from plant.”
“Omnis cellula e cellula” means
every cell from a cell.

3. How does an organism such as Amoeba produce offspring compared to a human?
Amoeba - one cell divides to create an entire organism.
Human - cells divide to repair, maintain, or become part of a multicellular organism ; gametes (half the chromosomes) are made for reproduction

4. What might be a disadvantage to the progeny of an Amoeba compared to the offspring of humans?
Offspring of humans have more variation
because gametes are continuously mixing chromosomes from different organisms while in Amoebas the organisms itself is copied and divided to make more which leads to less variation which is bad if the environment changes and the population is not suited for the change.

5. Vocab genome – all genetic information in a cell (organism)
chromosomes - packages of DNA molecules (46 in humans)
somatic cells - all body cells except reproductive cells
gametes - reproductive cells with half the # of chromosomes
chromatin - DNA-protein complex
6) sister chromatids - identical copies of chromosomes
7) centromere - the “waist” where sisters are connected
8) Mitosis - division of the nucleus (P,PM,M,A,T) which produces genetically equivalent cells
9) cytokinesis - division of the cytoplasm
10) Meiosis - division that produces gametes

6. Stages of the Cell Cycle

7. Interphase G1 - phase S - phase G2 - phase
Cell is performing normal cell functions while growing
S - phase
DNA replicates (copies)
G2 - phase
Organelles double in number to prepare for division

8. Prophase Spindle fibers (ropes) form
Centrioles (make spindles) move to opposite poles
Chromosomes become visible
Nuclear membrane and nucleolus breaks apart

9. Metaphase
Chromosomes line up along the equator (middle of the cell)

10. Anaphase
Chromatids (copies of chromosomes) separate and move to opposite poles

11. Telophase
Nuclear membrane forms around each group of chromosomes and the nucleolus reappears
Chromosomes unwind and seem to disappear
Spindle fibers degrade
Cytokinesis begins (pinches in)

12. Cytokinesis
The process by which the cytoplasm divides and one cell becomes two individual cells.

13. Purpose of Mitosis - Cell Division
Growth
Repair

14. During cell divison, parent cells must be able to:
Make a copy of all information (DNA)
Transfer one copy of this information (DNA) to each daughter cell so they get the same instructions
Provide each daughter cell with enough cellular machinery (organelles) in order to function

16. Things to think about:
Why is it important that DNA copies are distributed equally to the daughter cells?
Why is it important that each daughter cell receive all of the cellular organelles? (These include mitochondria, chloroplasts, Golgi apparatus, and endoplasmic reticulum.) Describe which processes might be affected if a daughter cell did not receive one of these organelles.

17. Cells need nutrients as building blocks for new biomolecules
Cells need nutrients as building blocks for new biomolecules. Other than nutrients, what product(s) of metabolism is provided for the cell? At what points during the stages of cell division are these products required?
What difficulties might arise for an organism if muscle cells or nerve cells are damaged?

18. Mitosis

19. Mitosis

20. Cytokinesis
Division of the cytoplasm

21. Mitosis Animation

22. More Vocab
mitotic spindle - fibers made of microtubules; attach to chromosomes
centrosome - non-membranous organelle; assembly of spindle microtubules starts
kinetochore - structure of protein and chromosomal DNA at the centromere; “walks” the chromosome down the microtubule
metaphase plate - the plane midway between the two poles where the chromomomes line-up during metaphase

23. What is the function of kinetochore and non-kinetochore microtubules?
kinetechore - “walk” the chromosomes to one pole
non-kinetechore - elongating the whole cell during anaphase

24. Animal vs. Plant Animal Plant cleavage;
cleavage furrow appears, deepens until cell is spit in two
Plant
cell plate;
vesicles from Golgi apparatus move to middle of cell

25. Binary Fission – “division in half”
What brings about the separation
of the two daughter cells?
Still a mystery …

26. Evolution of Mitosis

27. Regulation of the Cell Cycle
The cell cycle is driven by specific chemical signals in the cytoplasm.

28. 1970’s – Experimentation:
Two cells in different phases of the cell cycle are fused together. If one is in S while another in G1, the G1 immediately enters S.
Likewise, if one is undergoing Mitosis the second nucleus also enters Mitosis.

29. More Vocab
Cell Cycle Control System:
A cyclically operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle.
Checkpoint:
Point where stop and go-ahead signals regulate the cycle.
2 main regulatory molecules:
Protein kinases
Cyclins
Cdks:
proteins that drive the cell cycle and rise and fall depending on the concentration of cyclin.
MPF:
“maturation or M-phase promoting factor”
cyclin-Cdk complex
Triggers cells passage past the G2 checkpoint and into M-phase

30. Figure 12.14 – Campbell 6th Edition

31. Role of Cdk, cyclin, and MPF:
Binds to cyclin to form MPF
Cyclin:
Binds to Cdk to form MPF
MPF: Cdk + cyclin
Promotes mitosis by phosphorylating proteins
Breakdown of its own cyclin
Which is conserved? Why?
Cdk: It’s an enzyme so it’s reusable!

32. Kinetechore Involvement:
Kinetechores not yet attached to microtubules trigger a signal that delays the onset of anaphase by keeping the Anaphase Promoting Complex (APC) in an inactive state.
After all kinetochores are attached the “wait” signal ceases and APC becomes active.
Cyclin is broken down and proteins holding sister chromatids together are inactivated.

33. More Vocab: Growth Factor: PDGF: Density dependent inhibition:
Protein released by certain body cells that stimulate other cells to divide.
PDGF:
Stimulates the division of fibroblast cells; helps heal wounds.
Density dependent inhibition:
Crowded cells stop dividing.
Anchorage dependence:
Cells must be attached to substratum in order to divide.

35. Cancer Failure to exhibit density dependent inhibition
Failure to exhibit anchorage dependent inhibition
Cell cycle control system is abnormal
Manufactures its own growth factors or abnormal signal pathway

36. Last of the Vocab: Transformation: Tumor: Benign Tumor:
Process that converts normal cells to cancer cells
Tumor:
Mass of abnormal cells within otherwise normal tissue
Benign Tumor:
Remain at original site
Can be removed
Malignant Tumor:
Abnormal cells move to different regions, impair function of one or more organs; CANCER
Metastasis:
Spread of cancer cells to locations distant from the original site

37. Breast Cancer