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