lecture 14 biao ding

lecture 14 biao ding - Biol 113 AU2010 Lecture 14 Cell...

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1 Biol 113 AU2010 Lecture 14 Cell Cycle A. Overview: The key roles of cell division B. Cell division results in genetically identical or non-identical daughter cells C. The mitotic phase alternates with interphase in the cell cycle D. The eukaryotic cell cycle is regulated by a molecular control system E. Stop and go signs: Internal and external signals at the checkpoints A. Overview: The Key Roles of Cell Division The ability of organisms to reproduce best distinguishes living things from nonliving matter The continuity of life is based on the reproduction of cells, or cell division In unicellular organisms, division of one cell reproduces the entire organism Multicellular organisms depend on cell division for: Development from a fertilized cell Growth Repair Cell division is an integral part of the cell cycle , the life of a cell from formation to its own division B. Cell Division Results in Genetically Identical or Non-identical Daughter Cells Most cell division results in daughter cells with identical genetic information, DNA Somatic (non-reproductive) cell division in eukaryotes consists of: Mitosis , the division of the nucleus Cytokinesis , the division of the cytoplasm A special type of division, meiosis , produces nonidentical daughter cells (gametes, or sperm and egg cells) Meiosis yields nonidentical daughter cells that have only one set of chromosomes, half as many as the parent cell 1. Cellular Organization of the Genetic Material All the DNA in a cell constitutes the cell’s genome A genome can consist of a single DNA molecule (common in prokaryotic cells) or a number of DNA molecules (common in eukaryotic cells) DNA molecules in a cell are packaged into chromosomes Fig. 12-3 Every eukaryotic species has a characteristic number of chromosomes in each cell nucleus Somatic cells (nonreproductive cells) have two sets of chromosomes Gametes (reproductive cells: sperm and eggs) have half as many chromosomes as somatic cells Eukaryotic chromosomes consist of chromatin , a complex of DNA and protein that condenses during cell division Fig. 12-4 0.5 µ m Chromosomes Chromosome duplication (including DNA synthesis) Chromo- some arm Centromere Sister chromatids Separation of sister chromatids Centromere Sister chromatids DNA molecules In preparation for cell division, DNA is replicated and the chromosomes condense Each duplicated chromosome has two sister chromatids , which separate during cell division The centromere
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lecture 14 biao ding - Biol 113 AU2010 Lecture 14 Cell...

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