The Cell Cycle and Mitosis

Transcription

1 The Key Roles of Cell Division Chapter 1 The Cell Cycle and Mitosis Cell division Cellular reproduc-on An ability of organisms that best dis-nguishes living things from nonliving ma:er Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Unicellular organisms Cellular division reproduces the en-re organism Mul-cellular organisms depend on cell division for: Development from a fer-lized cell Growth Repair Cell cycle Cell Division Life of a cell from forma-on to its own division Cell division is an integral part Fig. 1- (a) Reproduction 100 µm 00 µm 0 µm (b) Growth and development (c) Tissue renewal 1

2 Genome All the DNA in a cell May be a single DNA molecule prokaryo-c cells or Many DNA molecules eukaryo-c cells Chromosomes Packaged DNA molecules in a cell One molecule of DNA equals one chromosome Each eukaryo-c species Has a characteris-c number of chromosomes in each cell nucleus Soma9c cells Non reproduc-ve cells have two of each type of chromosome Diploid 46 Germ cells Make Gametes Reproduc-ve cells: sperm and eggs Only one of each chromosome Haploid 3 Human average 51 million 45 million base pairs Chroma9n Complex of DNA and protein that condenses during cell division In Eukaryo-c chromosomes Typical DNA form when not ac-vely dividing Distribu9on of Chromosomes During Eukaryo9c Cell Division Prepara-on for cell division DNA is replicated and the chromosomes condense Sister chroma9ds Duplicated chromosome Two copies which separate during cell division Junc-on point of the duplicated chromosome, where the two chroma-ds are a:ached

3 Fig µm Chromosomes Types of Eukaryo9c Cell Division DNA molecules Eukaryo-c cell division consists of: Chromosome arm Chromosome duplication (including DNA synthesis) Mitosis Division of the duplicated genome Cytokinesis Sister chromatids Division of the cytoplasm Meiosis A varia-on of cell division for making gametes Separation of sister chromatids Sister chromatids Yields noniden-cal daughter cells only one set of chromosomes, half as many as the parent cell haploid Phases of the Cell Cycle Cell Cycle Interphase The cell cycle consists of Mito9c (M) phase mitosis and cytokinesis Interphase cell growth copying of chromosomes in prepara-on for cell division about 90% of the cell cycle can be divided into subphases: G1 phase first gap S phase Synthesis of duplicate DNA G phase second gap 3

4 Fig. 1-5 Mito9c Phase of the Cell Cycle Mitosis is conven-onally divided into five phases: S (DNA synthesis) G1 M MI (M ) T O T IC PHA SE s es si to ito Cy n ki is G Telophase Cytokinesis is well underway by late telophase Fig. 1-6 G of Interphase Fragments Nonkinetochore plate Spindle Centrosome at one pole Cleavage furrow Daughter chromosomes Nucleolus Nuclear 4

5 Interphase (G) G of Interphase Diffuse chroma-n Fragments Nonkinetochore duplicated state Nucleolus s-ll visible G of Interphase Chroma-n begins to G of Interphase condense begin to migrate G of Interphase Spindle begins to grow Fragments Nonkinetochore Fig. 1-6c Chromsomes fully condensed Nuclear membrane broken down of Interphase G establish poles Spindle fibers a:ach to kinetochores G of Interphase Fragments plate Nonkinetochore Chromsomes line up at metaphase plate Cleavage Nucleolus Single file furrow Guided by fibers Spindle Centrosome at one pole Daughter chromosomes Nuclear 5