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Chapter 14 Notes (Summer2011)

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Biological Sciences
Rosada Silva

BIOB11Summer2011 Chapter 14 Cellular Reproduction Cell Division o Cell division happens differently in eukaryotes than in prokaryoteso 2 distinct types mitosis and meiosis o Mitosis leads to cells that are genetically identical to their parent o Meiosis leads to production of cells with half of the genetic content of the parentfor sexual reproduction Cell Cycle o Series of stages that a cell goes through during the life of the cell o Consists of M phase and interphase o The M phase includes process of mitosis and cytokinesislasts about an hour or so o Interphase constitutes the majority of the cellit may extend for days weeks or longer Interphase o Interphase include G1 S and G2 periods o G1 takes place between the end of mitosis and the beginning of DNA replicationcell grows and carries out normal metabolism organelles duplicateo DNA replication occurs during the S phase o G2 occurs between the end of S phase and the beginning of mitosis cell grows and prepares for mitosis Cell Cycle Continued o There are 3 cell types o Specialized cells that have lost their ability to dividenerve cells o Cells that do not divide but can begin DNA synthesis when given the appropriate stimulusliver cells o Cells that divide frequentlystem cells have asymmetric cell division Cell Fusion Experiments o In 1970 cell fusion experiments were conductedo Cells were fused at different stages in the cell cycle o G1 phase and Mphase fusionpremature chromosomal compaction o G2 phase and M phase fusionpremature chromosomal compaction o S phase and M phase fusioncompacted chromatin but pulverized fragments instead of chromosomeso Transition from G2 to M phase was under positive controltransition was induced by some agentTransition to M phase o Entry of cell into M phase is initiated by a proteinmaturation promoting factor mpf o MPF has 2 subunitskinase and cyclin o Kinasephosphorylates serine and threonline residues of specific proteins o Cyclinregulatory subunit whose concentration rises and falls with each cell cycle o The kinase is only active when complexed with cyclin subunitwhen cyclin levels are high mpf activity is highcell enters M phase o Progression of cells into mitosis depends on an enzyme whose activity is to phosphorylate other proteinsactivity controlled by a subunit whose concentration is cell cycle stage dependent o MPF like enzymes are called cyclin dependent kinases Cdks Yeast Fission o Yeast cells are very useful in studying cell cycle
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