1. Chapter 12:
The Cell Cycle 1

3. Cell Division: Key Roles
Genome: cell’s genetic info
Somatic cells vs. Gametes
Chromosomes: condensed DNA (+ protein)
Diploid (2n): 2 chromosome sets; Haploid (1n): 1 set
Chromatin: Loose DNA-protein
Chromatids: replicated strands of a chromosome
Centromere: “waist” of sister chromatids
Mitosis: nuclear division
Cytokinesis: cytoplasm division
Meiosis: gamete cell division 3

4. Cell Division Purpose Unicellular organisms:
Division = reproduction
Multicellular organisms: division for
Development
Growth
Repair
Cell cycle: life of cell from formation to division

5. 100 µm (a) Reproduction Fig. 12-2a
Figure 12.2 The functions of cell division
(a) Reproduction

6. The Cell Cycle Interphase G1 phase: growth S phase: DNA synthesis
90% of cycle
G1 phase: growth
S phase: DNA synthesis
G2 phase: prep for cell division
Mitotic phase
Mitosis: nuclear division
Cytokinesis: cytoplasm division 6

7. Mitosis Prophase Prometaphase Metaphase Anaphase Telophase
BioFlix: Mitosis 7

8. BioFlix: Mitosis

9. Prophase Chromosomes visible Nucleoli disappear Sister chromatids
Mitotic spindle forms
Centrosomes move 9

10. Prometaphase Nuclear membrane fragments
Spindle interacts w/ chromosomes
Kinetochore develops 10

11. Metaphase Centrosomes at opposite poles Centromeres aligned
Kinetochores of sister chromatids attached to microtubules (spindle) 11

12. Anaphase Centromeres separate Chromosomes move to opposite poles
Each pole has complete chromosome set 12

13. Telophase Daughter nuclei form Nuclear envelopes arise
Chromatin becomes less coiled
Two new nuclei complete mitosis 13

14. Cytokinesis Cytoplasmic division Animals: Plants: cleavage furrow
cell plate
Animation: Cytokinesis
Video: Animal Mitosis
Video: Sea Urchin (Time Lapse) 14

15. 1 Prophase 2 Prometaphase 3 Metaphase 4 Anaphase 5 Telophase 10 µm
Fig
Nucleus
Chromatin
condensing
10 µm
Chromosomes
Cell plate
Nucleolus
Figure Mitosis in a plant cell 1
Prophase 2
Prometaphase 3
Metaphase 4
Anaphase 5
Telophase

16. Binary Fission How Proks (bacteria/archaea) reproduce/divide
Chromosome replicates
begins at the origin of replication
Two daughter chromosomes actively move apart
Cytokinesis occurs
Mitosis probably evolved from binary fission
Some seemingly intermediate protist cell division

17. Cell wall Origin of replication Plasma membrane E. coli cell Bacterial
Fig
Cell wall
Origin of
replication
Plasma
membrane
E. coli cell
Bacterial
chromosome
Two copies
of origin
Origin
Origin
Figure Bacterial cell division by binary fission

18. Cell Cycle Control System
Specific checkpoints where cell cycle stops
Waits for “go” signal
G1 is first/most important
If no signal cell enters G0, will not divide
G2 checkpoint followed by mitosis
Cyclin builds up in cell, joined with CDK = MPF
MPF = Mitosis Promoting Factor
M checkpoint = kinetochore w/ chromosomes to cont.

19. G1 checkpoint Control system S G1 G2 M M checkpoint G2 checkpoint
Fig
G1 checkpoint
Control
system S G1 G2 M
Figure Mechanical analogy for the cell cycle control system
M checkpoint
G2 checkpoint

20. M G1 S G2 M G1 S G2 M G1 Fig. 12-17 MPF activity Cyclin concentration
Time
(a) Fluctuation of MPF activity and cyclin concentration during
the cell cycle G1 S
Cdk
Figure Molecular control of the cell cycle at the G2 checkpoint
Cyclin accumulation M
Degraded
cyclin G2 G2
Cdk
Cyclin is
degraded
checkpoint
Cyclin
MPF
(b) Molecular mechanisms that help regulate the cell cycle

21. Cell Cycle regulation Growth factors Density-dependent inhibition
Anchorage dependence 21

22. Cancer
Transformation
Tumor: benign or malignant
Metastasis 22

23. You should now be able to:
Describe the structural organization of the prokaryotic genome and the eukaryotic genome
List the phases of the cell cycle; describe the sequence of events during each phase
List the phases of mitosis and describe the events characteristic of each phase
Draw or describe the mitotic spindle, including centrosomes, kinetochore microtubules, nonkinetochore microtubules, and asters
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

24. Compare cytokinesis in animals and plants
Describe the process of binary fission in bacteria and explain how eukaryotic mitosis may have evolved from binary fission
Explain how the abnormal cell division of cancerous cells escapes normal cell cycle controls
Distinguish between benign, malignant, and metastatic tumors
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings