3.3 The Cell Cycle A.Introduction • Set of stages that take place between the time a cell divides and the time the.
Download ReportTranscript 3.3 The Cell Cycle A.Introduction • Set of stages that take place between the time a cell divides and the time the.
3.3 The Cell Cycle A.Introduction • Set of stages that take place between the time a cell divides and the time the daughter cell divides • Controlled by external and internal signals • Apoptosis (cell death) occurs at a restriction checkpoint if the cell did not complete mitosis and is abnormal • Some specialized cells no longer go through the cell cycle - muscle cells and nerve cells B.Cell Cycle Stages - Interphase • Cell is not dividing, but is preparing to divide • The cell carries on regular activities • Three phases a.G1 phase – cell doubles number of organelles and accumulates materials used for DNA synthesis b.S phase – “synthesis” phase; DNA replication occurs c. G2 phase – cell synthesizes proteins that will assist cell division and completes replication of centrioles The Cell Cycle Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. C.Major events during interphase • Replication of DNA a. Before replication, the two strands of DNA are hydrogen bonded together b. Parental DNA strands unwind (hydrogen bonds are broken) c. New complimentary nucleotides pair with nucleotides in the parental DNA strands and DNA polymerase joins the new nucleotides d. When replication is complete, two identical double helix molecules have been formed e. Each strand of this double helix is equivalent to a chromatid; held together by the centromere Overview of DNA Replication Ladder configuration & DNA replication Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 2.Protein synthesis a. DNA also serves as a template for RNA formation and protein construction b. Two steps involved in protein synthesis are: 1) Transcription – formation of mRNA 2) Translation – involves mRNA, tRNA, and rRNA; specifies the order of amino acids in a polypeptide Protein Synthesis Process Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. D.The Cell Cycle – Mitotic Stage • M-stage – nuclear division stage divided into 4 phases a. Prophase 1)The centrioles near nucleus begin moving towards opposite ends of nucleus 2)Spindle fibers appear between the centrioles 3)Nuclear envelope begins to fragment 4)Nucleolus begins to disappear 5)Chromosomes appear randomly and attached to spindle fibers by their centromere M-stage, cont b. Metaphase 1)Spindle is fully formed 2)Chromosomes are aligned at the equator c. Anaphase 1)Centromere splits 2)Sister chromatids separate (now called chromosomes) 3)Chromosomes move toward opposite poles of the spindle (toward centrioles) 4)Some spindle fibers push the chromosomes apart while others pull them toward the poles M-stage, cont d. Telophase 1) Chromosomes become chromatin 2) Spindle disappears and nucleoli appear 3) Nuclear envelope reassembles and two daughter cell nuclei can be observed 2.The Cell Cycle - Cytokinesis a.Cytokinesis – division of the cytoplasm and organelles b.Begins in anaphase and completes in telophase c. Actin filaments form a ring around the equator that contracts, pinching the cell in half Mitotic Stage of the Cell Cycle Mitosis in a whitefish embryo Please note that due to differing operating systems, some animations will not appear until the presentation is viewed in Presentation Mode (Slide Show view). You may see blank slides in the “Normal” or “Slide Sorter” views. All animations will appear after viewing in Presentation Mode and playing each animation. Most animations will require the latest version of the Flash Player, which is available at http://get.adobe.com/flashplayer. 3.Importance of mitosis a. Maintains chromosome number b. Each cell in our body is genetically identical c. Each cell type has certain genes turned on and others turned off to give the different types of body cells d. Important to the growth and repair of multicellular organisms E.Meiosis • Known as reduction division because the chromosome number is cut in half • The four phase of mitosis are repeated twice with some changes in the steps that occur • The gametes (ova and sperm) have half the chromosomes of normal body cells so that when they join to form the zygote, the chromosome number is correct for that organism.