bio chp 15 notes - Chapter15 CELL CYCLE MITOSIS AND MEIOSIS...

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Chapter 15 03:36 CELL CYCLE, MITOSIS AND MEIOSIS Learning Goals: - prokaryotic cell division - the cell cycle - mitosis: purpose, stages and problems - meiosis: purpose, stages and problems Cell Division in Prokaryotes - Replication occupies most of the cell cycle in rapidly dividing prokarytic cells - Replicated chromosomes are distributed actively to the halves of prokaryotic cells - Mitosis has evolved from binary fission
Cell Cycle Regulation - Cyclins and cyclin-dependent kinases: internal control that directly regulate cell division - Complexes of cyclin and a cyclin-dependent protein kinase (CDK) directly regulates cell cycle - CDK is activated when combined with a cyclin adds phosphate groups to target proteins, activating them Cell Cycle Control - activated proteins trigger the cell to progress to the next cell cycle stage - each major stage of the cell cycle: begins with activation of one or more cyclin/CDK complexes ends with deactivation of complexes by breakdown of cyclins
Internal Controls - important internal controls create checkpoints ensures that the reactions of one stage are complete before cycle proceeds to next stage External Controls - based on surface receptors that recognize and bind signals peptide hormones and growth factors surface groups on other cells molecules of the extracellular matrix - binding triggers internal reactions that speed, slow, or stop cell division Cancer - control of cell division is lost cells divide continuously and uncontrollably form rapidly growing mass of cells that interferes with body functions - cancer cells break loose from their original tumor (metastasize) from additional tumors in other parts of the body Mitotic Cell Division - equal separation (segregation) of replicated DNA molecules - delivery to daughter cells two new cells, same information as parent cells - mitosis is the basis for
growth and maintenance of body mass in multi-celled eukaryotes “reproduction” of many single-celled eukaryotes Mitosis has one purpose: - to enable cells to generate new, genetically identical cells - there are two different reasons for this need: growth replacement Chromosomes - DNA of eukaryotic cells is divided among individual, linear chromosomes located in cell nucleus - ploidy of a cell or species - number of chromosomes diploid (2n) haploid (n) Sister Chromatids - DNA replication and duplication of chromosomal proteins produces two exact copies (sister chromatids) - chromosome segregation occurs during cell division The Mitotic Cell Cycle

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