Chapter 12 Notes
Chapter 12 Notes BIOl 1020-003
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This 5 page Class Notes was uploaded by Crystal Boutwell on Friday October 16, 2015. The Class Notes belongs to BIOl 1020-003 at Auburn University taught by Dr. Zhong in Fall 2015. Since its upload, it has received 36 views. For similar materials see Principles of Biology in Biology at Auburn University.
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Date Created: 10/16/15
Chapter Twelve The Cell Cycle Compiled by Crystal Boutwell I 11 Introduction A the reproduction of cells i Important roles 1 When a prokaryotic cell divides it is reproducing 2 Multicellular eukaryotes organisms develop from a single cell B the life of a cell from the time it is first formed during division of a parent cell to its own division into two daughter cells Cell Division results in genetically identical daughter cells A Process A dividing cell will copy its DNA send the two copies to opposite poles of the cell and then split into two daughter cells B a cell s genetic information i Prokaryotic A single DNA molecule ii Eukaryotic many DNA molecules C a package of DNA molecules D A building block of chromosomes i So if your mom sends you a care package from home and it has toothpaste and candy and tissues and a DVD the entire package inside the box is the chromosome The individual pieces of the package are the chromatin Think chromosome is more packed up and chromatin is more free E nonreproductive cells i The human cell has 46 chromosomes 2 sets of 23 chromosomes F reproductive cells sperm and egg i The human cell has one set of 23 chromosomes G When a cell is not dividing the form of each chromosome is a long thin chromatin fiber H After DNA replication and during cell division the chromatin fiber coils and becomes very condensed which makes the chromosomes very thick I after DNA duplication each duplicated chromosome has two sister chromatids These are joined copies of the original chromosome J a region of chromosol DNA where the chromatid is attached most closely to its sister chromatid Sister chromatids can also be attached all along their bodies by sister chromatid cohesion i Later in the cell division process forces will separate the two sister chromatids at the centromere and create two separate chromosomes which will each be distributed to a separate daughter cell K Each new nucleus of the daughter cells will receive chromosomes identical to the parent cell L the process of dividing the genetic material in the nucleus M the process of dividing the cytoplasm N 1 cell 9 mitosis cytokinesis 9 two identical cells 0 Meiosis the division of sex cells 111 The Cell cycle the Mitotic Phase and Interphase A Phases of the cell cycle a Prophase b Prometaphase c Metaphase d Anaphase e Telophase 3 Shortest part of the cell cycle 1 Much longer than mitotic phase 2 Accounts for 90 of the yle 3 Divided into three subphases a G1 phase cell growth b S phase duplication of the chromosomes and continued cell growth 0 G2 phase continued growth and preparations for cell division iii Usually take about 24 hours iv Some cells divide very rarely or not at all and spend their time in the G0 phase 1 EX nerve cell B What is the i Very important to mitosis ii Forms in the cytoplasm during prophase iii Made of microtubules and proteins iv Destroys other microtubules in the cell while forming and uses them to build itself C a subcellular region containing material that functions throughout the ell cycle to organize that cell s microtubules i During Interphase a single centrosome will duplicate and stay near the nucleus ii During prophase the two centrosomes will move apart and spindle fiber will start to grow from them iii By the end of prometaphase the two centrosomes are at opposite ends of the cell D a radial array of short microtubules extending from each centrosome E a structure made of proteins that assemble on each centromere of sister chromatids 2 They face opposite directions on the chromosome 1 ii iii iv V1 pulling each one in opposite directions During prometaphase spindle microtubules attach to the kinetochores The spindle microtubules start to play tug of war with the kinetochores At metaphase the centromeres of all the duplicated chromosomes are lined up in the middle of the centrosome s poles at an imaginary line called a metaphase plate seperase During Anaphase the sister chromatids separate using an enzyme called Both sister chromatids become individual chromosomes once separated The chromosomes are reeled in towards the poles Prophase Prometaphase Metaphase Anaphase Telophase Chromatin nuclear centrosomes Shortest stage two daughter fibers coil and envelope are officially at Cohesion nuclei form and condense into fragments opposite ends of proteins are nuclear chromosomes microtubules cell cleaved pulling envelopes form Nucleoli invade nuclear chromosomes the two sister nucleoli disappear area arrive at the chromatids reappear Each kinetochores metaphase plate apart chromosomes chromosome form on daughter loosen appears as two chromatids of chromosomes spindle identical sister chromosomes move toward microtubules are chromatids microtubules opposite ends of depolymerized joined at their attach to the the cell reeled Mitosis is centromere kinetochores in complete Mitotic spindle playing tug of Cell elongates Cytokinesis begins to form war with the follows Centrosomes chromosomes move away from each other F Cytokinesis i Animal Cells a shallow groove in the cell surface near the old metaphase plate A contractile ring in the cytoplasm pinching of the cell in two Forms two cells ii Plant Cells 1 Cell walls 2 No cleavage furrow 3 During telophase vesicles from Golgi apparatus move long microtubules to the middle of the cell These produce a cell plate 4 The cell plate enlarges until it fuses with the plasma membrane producing two daughter cells i Bacteria ii The cell grows to double its size and divides to form two cells iii DNA replicates at a specific place on the chromosome called the origin of replication iv Cell elongates during replication v Plasma membrane pinches inward dividing in half vi Difference bacteria don t have mitotic spindles or microtubules IV Regulating the Eukaryotic cell A Frequency of cell division is varied depending on the type of cell B a cyclically operating set of molecules in the cell that both triggers and coordinates key events in the cell cycle C Checkpoint a control point in the cell cycle where stop and goahead signals can regulate the cycle i Found in G1 G2 and M phases D enzymes that activate or inactivate other proteins by phosphorylating them i To be active a kinase must be attached to a a protein that gets its name from its cyclically uctuating concentration in the cell ii Cyclindependent kinases Cdks E G1 checkpoint restriction point i Most important checkpoint ii Decides here whether or not it will divide F M phase checkpoint i Anaphase does not begin until all the chromosomes are properly attached to the spindle at the metaphase plate was G a protein released by certain cells that stimulates other cells to divide H crowded cells stop dividing i Effect of an external factor on cell division I when cells must be attached to a substratum such as the inside of a ask to divide J Cancer Cells i Loss of cell cycle controls ii immortal or can go on dividing forever whereas normal cells will not iii Transformation causes cells to behave like cancer cells and divide indefinitely iv Benign tumor if abnormal cells remain at the original site if they have too few genetic and cellular changes to survive elsewhere v Malignant tumor cells whose genetic and cellular changes enable them to spread to new tissues and impair the functions of one or more organs vi Metatasis the spread of cancer cells to locations distant from their original site
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