100 µm200 µm 20 µm (a) Reproduction (b) Growth and development (c) Tissue renewal 1

20 µm 2

0.5 µmChromosomes Chromosome duplication (including DNA synthesis) Chromo- some arm Centromere Sister chromatids DNA molecules Separation of sister chromatids Centromere Sister chromatids 3

S (DNA synthesis) MITOTIC (M) PHASE Mitosis Cytokinesis G1G1 G2G2 4

G 2 of Interphase Centrosomes (with centriole pairs) Chromatin (duplicated) Nucleolus Nuclear envelope Plasma membrane Early mitotic spindle Aster Centromere Chromosome, consisting of two sister chromatids Prophase Prometaphase Fragments of nuclear envelope Nonkinetochore microtubules Kinetochore microtubule Metaphase plate Spindle Centrosome at one spindle pole Anaphase Daughter chromosomes Telophase and Cytokinesis Cleavage furrow Nucleolus forming Nuclear envelope forming 5

Microtubules Chromosomes Sister chromatids Aster Metaphase plate Centrosome Kineto- chores Kinetochore microtubules Overlapping nonkinetochore microtubules Centrosome 1 µm 0.5 µm 6

EXPERIMENT Kinetochore RESULTS CONCLUSION Spindle pole Mark Chromosome movement Kinetochore Microtubule Motor protein Chromosome Tubulin subunits 7

Cleavage furrow 100 µm Contractile ring of microfilaments Daughter cells (a) Cleavage of an animal cell (SEM)(b) Cell plate formation in a plant cell (TEM) Vesicles forming cell plate Wall of parent cell Cell plate Daughter cells New cell wall 1 µm 8

Chromatin condensing Metaphase AnaphaseTelophase Prometaphase Nucleus Prophase Nucleolus Chromosomes Cell plate 10 µm 9

Origin of replication Two copies of origin E. coli cell Bacterial chromosome Plasma membrane Cell wall Origin 10

(a) Bacteria Bacterial chromosome 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 1 Experiment 2 EXPERIMENT RESULTS SG1G1 M G1G1 M M S S When a cell in the S phase was fused with a cell in G 1, the G 1 nucleus immediately entered the S phase—DNA was synthesized. When a cell in the M phase was fused with a cell in G 1, the G 1 nucleus immediately began mitosis—a spindle formed and chromatin condensed, even though the chromosome had not been duplicated. 12

S G1G1 M checkpoint G2G2 M Control system G 1 checkpoint G 2 checkpoint 13

G1G1 G0G0 G 1 checkpoint (a)Cell receives a go-ahead signal G1G1 (b) Cell does not receive a go-ahead signal 14

M G1G1 S G2G2 M G1G1 SG2G2 M G1G1 MPF activity Cyclin concentration Time (a) Fluctuation of MPF activity and cyclin concentration during the cell cycle Degraded cyclin Cdk G1G1 S G2G2 M G2G2 checkpoint Cyclin is degraded Cyclin MPF (b) Molecular mechanisms that help regulate the cell cycle Cyclin accumulation 15

Petri plate Scalpels Cultured fibroblasts Without PDGF cells fail to divide With PDGF cells prolifer- ate 10 µm 16

Anchorage dependence Density-dependent inhibition (a) Normal mammalian cells (b) Cancer cells 25 µm 17

Tumor A tumor grows from a single cancer cell. Glandular tissue Lymph vessel Blood vessel Metastatic tumor Cancer cell Cancer cells invade neigh- boring tissue. Cancer cells spread to other parts of the body. Cancer cells may survive and establish a new tumor in another part of the body