1. AP Biology Crosby High School
Mitosis
AP Biology
Crosby High School

2. Cell Division Reproduction, Growth, and Repair Basic steps:
Duplicates DNA
Copies split to opposite ends
Cell splits
2 Daughter Cells formed

3. Genome Prokaryote vs. Eukaryote Prokaryote: Single strand of DNA
More than on strand of DNA
Each species has a specific number of chromosomes
Human Somatic Cells: 46 chromosomes (Diploid)
Human Gametic Cells: 23 chromosomes (Haploid)

4. Structures and Overview of Splitting
DNA strand wrapped around proteins
Chromatin: DNA/Protein complex
Condenses to form Chromosomes
Copied forming Sister Chromatids
Chromatids joined at Centromere
Chromatids separate in Mitosis
Cytoplasm separates in Cytokinesis

5. Interphase 90% of Cell Cycle Consists of Three Phases
G1 Phase (Gap one)
Growth of the cell
S Phase (Synthesis)
DNA replication
G2 Phase (Gap two)

6. Mitotic Phase “Please Pour Me Another Tequila” Prophase Prometaphase
Anaphase
Telephase

7. Mitotic Spindle Centrosomes form spindles
Centriole pairs inside Centrosomes
Centrosomes replicate near nucleus
Two centrosomes grow spindle microtubules
Separate to opposite ends of the cell
Spindles “play tug-o-war” at Kinetochores
Pull both directions until chromosomes reach metaphase plate

8. Mitotic Spindles and Anaphase
Proteins holding sister chromatids deactivate
Chromosomes “walk” along microtubules
Microtubules shorten by depolymerizing
Nonkinetochore microtubules lengthen the cell

9. Cytokinesis Begins with Cleavage furrow Actin and Myosin contraction
Differences of Plant Cytokinesis
Vesicles from Golgi form cell plate
Plate grows and fuses with plasma membrane
Cell wall materials accumulate and form cell wall

10. Mitosis: Evolution of Binary Fission?
Prokaryotes have no spindle fibers
Origin of Replication replicates in opposite directions
Plasma membrane grows inward
Dinoflagellates and Diatoms
Unicellular algae
Divides with nuclear envelope intact

11. Cell Cycle Regulation Controlled on the molecular level by signals
Fused cells could force Mitosis
Fused to have two nuclei
Performed same function
Cell cycle control system
Internal signals
External signals

12. Cell Cycle Checkpoints
3 major checkpoints
G1(Restriction point)
Begins the S phase
Decides whether the cell will divide or not
Yes: Enters S phase
No: Enters G0 phase G2
Precedes mitosis M
Has mitosis completed?

13. Cyclin and Cyclin Dependent Kinases
Fluctuates in the cell
When present bind to Cdks for activation
G1 checkpoint contains 3 Cdks and several cyclins
Maturation Promoting Factor (MPF)
Past G2
Initiates Mitosis by phosphorylating proteins
Turns itself off by degrading cyclin
Remains present in inactive form

14. Internal Signals Messages received from Kinetochores
Anaphase does not begin until all kinetochores are attached to a spindle fiber
Signal comes from non-attached
Anaphase promoting complex (APC) inactive
Active: APC triggers breakdown of cyclin and deactivation of sister chromatids

15. External Signal Platelet-derived Growth Factor (PDGF)
Fibroblasts have PDGF receptors
Heals wounds
Density dependent Inhibition
Cells form one layer IN CULTURE and stop
Continue to grow when cells are removed
Anchorage Dependence
Must be attached to substratum

16. Cancer Uncontrolled cell growth Control point malfunctions
Cell continues to grow beyond inhibition
HeLa cells have been growing since 1951

17. Onset of Cancer Transformation: cell malfunctions
If not destroyed it becomes a tumor
Benign: Remains at origin
Malignant: invasive enough to impair organs
Cells lose function and inhibition
Cells lose attachment and spread
Spread through lymphatic or blood vessels
Metastasis

18. Cancer

19. Mitosis

20. Mitosis (cont.)

21. Spindle Shortening

22. Cyclin and MPF