100 µm 200 µm 20 µm
(a) Reproduction (b) Growth and (c) Tissue renewal development
1 20 µm
2 0.5 µm Chromosomes DNA molecules
Chromo- Chromosome some arm duplication (including DNA synthesis) Centromere
Sister chromatids
Separation of sister chromatids
Centromere
Sister chromatids 3 G S 1 (DNA synthesis)
G2
4 G2 of Interphase Prophase Prometaphase Metaphase Anaphase Telophase and Cytokinesis Centrosomes Chromatin Early mitotic Aster Centromere Fragments Nonkinetochore Metaphase Cleavage Nucleolus (with centriole (duplicated) spindle of nuclear microtubules plate furrow forming pairs) envelope
Daughter Nuclear Nucleolus Nuclear Plasma Chromosome, consisting Kinetochore Kinetochore Spindle Centrosome at chromosomes one spindle pole envelope envelope membrane of two sister chromatids microtubule forming
5 Aster Centrosome Sister chromatids Microtubules Chromosomes Metaphase plate
Kineto- chores
Centrosome 1 µm
Overlapping nonkinetochore Kinetochore microtubules microtubules
0.5 µm 6 EXPERIMENT Kinetochore
Spindle pole
Mark
RESULTS
CONCLUSION
Chromosome movement Kinetochore
Motor Tubulin Microtubule protein subunits Chromosome 7 Vesicles Wall of 1 µm 100 µm forming parent cell Cleavage furrow cell plate Cell plate New cell wall
Contractile ring of Daughter cells microfilaments Daughter cells (a) Cleavage of an animal cell (SEM) (b) Cell plate formation in a plant cell (TEM)
8 Nucleus Chromatin 10 µm Nucleolus condensing Chromosomes Cell plate
1 Prophase 2 Prometaphase 3 Metaphase 4 Anaphase 5 Telophase
9 Cell wall Origin of replication Plasma membrane E. coli cell Bacterial Two copies chromosome of origin
Origin Origin
10 Bacterial chromosome
(a) Bacteria
Chromosomes
Microtubules
Intact nuclear envelope (b) Dinoflagellates
Kinetochore microtubule
Intact nuclear envelope
(c) Diatoms and yeasts
Kinetochore microtubule
Fragments of nuclear envelope (d) Most eukaryotes 11 EXPERIMENT Experiment 1 Experiment 2
S G1 M G1
RESULTS
S S M M When a cell in the When a cell in the S phase was fused M phase was fused with with a cell in G1, the G1 a cell in G1, the G1 nucleus immediately nucleus immediately entered the S began mitosis—a phase—DNA was spindle formed and synthesized. chromatin condensed, even though the chromosome had not been duplicated. 12 G1 checkpoint
Control system S G1
M G2
M checkpoint
G2 checkpoint 13 G0
G1 checkpoint
G1 G1
(a) Cell receives a go-ahead (b) Cell does not receive a signal go-ahead signal
14 M G1 S G2 M G1 S G2 M G1
MPF activity Cyclin concentration
Time (a) Fluctuation of MPF activity and cyclin concentration during the cell cycle Cyclin accumulation
Cdk
Degraded cyclin G2 Cdk Cyclin is checkpoint degraded
Cyclin MPF
(b) Molecular mechanisms that help regulate the cell cycle 15 Scalpels
Petri plate
Without PDGF With PDGF cells fail to divide cells prolifer- ate
Cultured fibroblasts 10 µm
16 Anchorage dependence
Density-dependent inhibition
Density-dependent inhibition
25 µm 25 µm
(a) Normal mammalian cells (b) Cancer cells
17 Lymph vessel Tumor Blood vessel
Cancer Glandular cell tissue Metastatic tumor 1 A tumor grows 2 Cancer cells 3 Cancer cells spread 4 Cancer cells may from a single invade neigh- to other parts of survive and cancer cell. boring tissue. the body. establish a new tumor in another part of the body.
18