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