BioNotesChapter12TheCellCycle.pdf BIOL 1020 - 001
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This 3 page Class Notes was uploaded by Emma Karlson on Thursday October 22, 2015. The Class Notes belongs to BIOL 1020 - 001 at Auburn University taught by Dr. Zanzot in Summer 2015. Since its upload, it has received 16 views. For similar materials see Principles of Biology in Biological Sciences at Auburn University.
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Date Created: 10/22/15
Chapter 12 The Cell Cycle The Key Roles of Cell Division 0 The ability of organisms to produce more of their own kind best distinguishes living things from nonliving matter 0 The continuity of life is based on the reproduction of cells or cell division 0 There are three main reasons cell divides o Reproduction 0 Growth and Development 0 Tissue renewal Concept 121 Most cell division results in genetically identical daughter cells 0 Most cell division results in daughter cells with identical genetic information DNA 0 The exception is meiosis a special type of division that can produce sperm and egg cells Cellular Organization of the Genetic Material 0 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 0 DNA molecules in a cell are packaged into chromosomes Chromatin Chromosomes Somatic Cells non reproductive cells 2n Gametes reproductive cells sperm and eggs n o In humans n 23 o In chimpanzees n24 o In fruit ies n4 0 Adder s tongue fern n630 During cell division the two sister chromatids of each duplicated chromosome separate and move into two nuclei 0 Once separate the chromatids are called chromosomes 0 Eukaryotic cell division consist of o Mitosis the division of the genetic material in the nucleus 0 Cytokinesis the division of the cytoplasm In animals gametes are produced by a variation of cell division called meiosis Meiosis yields nonidentical daughter cells that have half as many chromosomes as the parent cell Phases of the Cell Cycle 0 The cell cycle consists of o Mitotic M phase mitosis and cytokinesis o Interphase cell growth and copying of chromosomes in preparation for cell division 61 S 62 Mitosis Cytokinesis The Mitotic Spindle A Closer Look 0 The mitotic spindle is a structure made of microtubules that controls chromosome movement during mitosis In animal cells assembly of spindle microtubules begins in the centrosome the microtubuleorganizing center 0 The centrosome replicates during interphase forming two centrosomes that migrate to opposite ends of the cell during prophase and prometaphase An aster a radical array of short microtubules extends from each centrosome The spindle includes the centrosomes the spindle microtubules and the asters The Evolution of Mitosis Since prokaryotes evolved before eukaryotes mitosis probably evolved from binary fusion 0 Certain protists exhibit types of cell division that seems intermediate between binary ssion and mitosis Concept 123 The Eukaryotic cell cycle is regulated by a molecular control system 0 The frequency of cell division varies with the type of cell Theses differences result from regulation at the molecular level 0 Cancer cells manage to escape the usual controls on the cell cycle The Cell Cycle Control System 0 The cell cycle appears to be driven by speci c chemical signals present in the cytoplasm Some evidence for this hypothesis comes from experiments in which cultured mammalian cells at different phases of the cell cycle were fused to form a single cell with two nuclei The Cell Cycle Clock Cyclins and CyclinDependent Kinases Two types of regulatory proteins are involved in cell cycle control cyclins and cyclindependent kinases Cdks The activity of a Cdk rises and falls with changes in concentration of its cyclin partner 0 MPF maturationpromoting factor is a cyclinCdk complex that triggers a cell s passage past the Gz checkpoint into the M phase 0 Most cells also exhibit anchorage dependence to divide they must be attached to a substratum Densitydependent inhibition and anchorage dependence check the growth of cells at an optimal density 0 Cancer cells exhibit neither type of regulation of their division Loss of Cell Cycle Controls in Cancer Cells Cancer cells do not respond normally to the body s control mechanisms Cancer cells may not need growth factors to grow and divide 0 They may make their won growth factor 0 They may convey a growth factor s signal without the presence of the growth factor 0 They may have an abnormal cell cycle control system A normal cell is converted to a cancerous cell by a process called transformation Cancer cells that are not eliminated by the immune system form tumors masses of abnormal cells within otherwise normal tissue lf abnormal cells remain only at the original site the lump is called a benign tumor Malignant tumors invade surrounding tissues and can metastasize exporting cancer cells to other parts of the body where they may form additional tumors Localized tumors may be treated with highenergy radiation which damages the DNA in the cancer cells To treat metastatic cancers chemotherapies that target the cell cycle may be used Recent advances in understanding the cell cycle and cell cycle signaling have led to advances in cancer treatment Coupled with the ability to sequence the DNA of cells in a particular tumor treatments are becoming more personalized
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