Ch 12 BIOL 221 Cell Cycle and Mitosis The Key Roles of Cell Division Cell division Cellular reproduc2on An ability of organisms that best dis2nguishes living things from nonliving ma:er Cell Division Unicellular organisms Cellular division reproduces the en2re organism Mul2cellular organisms depend on cell division for: Development from a fer2lized cell Growth Repair Cell cycle Life of a cell from forma2on to its own division Cell division is an integral part 100 µm 200 µm 20 µm (a) Reproduction (b) Growth and development (c) Tissue renewal 1
Cellular Organiza>on of the Gene>c Material Genome All the DNA in a cell May be a single DNA molecule prokaryo2c cells or Many DNA molecules eukaryo2c cells Chromosomes Packaged DNA molecules in a cell One molecule of DNA equals one chromosome Human average 51 million - 245 million base pairs per chromosome Each eukaryo2c species Has a characteris2c number of in each cell nucleus Soma>c cells Non- reproduc2ve cells Germ cells Cellular Organiza>on of the Gene>c Material have two of each type of chromosome Diploid - 46 Make Gametes Reproduc2ve cells: sperm and eggs Only one of each chromosome Haploid - 23 Cellular Organiza>on of the Gene>c Material Chroma>n Complex of DNA and protein that condenses during cell division In Eukaryo2c Typical DNA form when not ac2vely dividing 2
Chromosome Distribu>on During Eukaryo>c Cell Division Prepara2on for cell division DNA is replicated and the condense Sister chroma>ds Duplicated chromosome Two copies which separate during cell division Junc2on point of the duplicated chromosome, where the two chroma2ds are a:ached Fig. 12-4 0.5 µm Chromosomes DNA molecules Chromosome arm Chromosome duplication (including DNA synthesis) Sister chromatids Separation of sister chromatids Sister chromatids Eukaryo2c cell division consists of: Mitosis Division of the duplicated genome Cytokinesis Meiosis Types of Eukaryo>c Cell Division Division of the cytoplasm A varia2on of cell division for making gametes Yields noniden2cal daughter cells Only one set of, half as many as the parent cell Haploid 3
Phases of the Cell Cycle The cell cycle consists of 2 phases Mito>c (M) phase mitosis and cytokinesis Interphase cell growth copying of in prepara2on for cell division Phases of the Cell Cycle - Interphase Interphase about 90% of the cell cycle can be divided into subphases: G 1 phase first gap S phase Synthesis of duplicate DNA G 2 phase second gap G 1 MITOTIC (M) PHASE Cytokinesis Mitosis S (DNA synthesis) G 2 Phases of the Cell Cycle - Mito>c Phase Mitosis is conven2onally divided into five phases: Anaphase Telophase Cytokinesis is well underway by late telophase PLAY 4
Fig. 12-6 G 2 of Interphase Anaphase Telophase and Cytokinesis Centrosomes Chromatin Early mitotic Aster Fragments Nonkinetochore (with centriole (duplicated) spindle of nuclear s plate Plasma membrane Spindle Centrosome at Interphase (G2) Diffuse chroma2n G 2 of Interphase Centrosomes Chromatin (with centriole (duplicated) duplicated state Early mitotic Chromosomes Aster not Fragments visible Nonkinetochore spindle of nuclear s under light microscope G 2 of Interphase s2ll present Plasma membrane 5
Chroma2n begins Centrosomes to condense begin to migrate Spindle begins to Chromatin Centrosomes (with centriole grow (duplicated) Early mitotic Aster spindle Fragments of nuclear Nonkinetochore s Plasma membrane Chromsomes fully condensed membrane broken down Centrosomes establish poles Spindle fibers a:ach to kinetochores Chromatin Centrosomes (with centriole (duplicated) Early mitotic Aster spindle Plasma membrane Fragments of nuclear Nonkinetochore s Fig. 12-6c Chromosomes line up at metaphase plate plate Anaphase Single file Telophase and Cytokinesis Guided by spindle fibers Spindle Centrosome at Anaphase Telophase and Cytokinesis 6
Fig. 12-6c Anaphase Sister chroma2ds separate Now Anaphase Telophase and Cytokinesis daughter plate Migrate to poles Anaphase Telophase and Cytokinesis Spindle fibers shorten Spindle Centrosome at Fig. 12-6c Telophase reach poles Begin to Anaphase Telophase and Cytokinesis decondense plate membranes form Anaphase Telophase and Cytokinesis Cytokinesis begins forms Spindle Centrosome at Mito>c spindle The Mito>c Spindle: A Closer Look Apparatus of s that controls chromosome movement during mitosis Centrosome Microtubule organizing center Consists of two centrioles During prophase assembles spindle s The centrosome replicates two centrosomes migrate to opposite ends of the cell spindle s grow out from them 7