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UT Knoxville BIOL 140 - Chapter 11

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Chapter 11 – The Cell CycleIntroduction to Cell DivisionContrasting Mitosis and MeiosisFunctions of MitosisWhat Is a Chromosome?Slide 6Chromosomes Change before and during MitosisChromosome ReplicationSlide 9M Phase and InterphaseInterphase – S PhaseInterphase – Gap PhasesThe Cell CycleSlide 14Mitosis OverviewChromosomes Change during the Cell CycleEvents in MitosisSlide 18ProphasePrometaphaseMetaphaseAnaphaseTelophaseSlide 24Slide 25CytokinesisDifferent Cell Types Undergo Cytokinesis DifferentlySlide 28Slide 29How Do Chromosomes Move during Mitosis?Slide 31Slide 32Control of the Cell CycleMitosis-Promoting Factor Induces MitosisCyclin Concentration Regulates MPF ConcentrationSlide 36MPF ActivationMPF DeactivationCell-Cycle CheckpointsG1 CheckpointWill a Given Cell Pass the G1 Checkpoint?G2 CheckpointMetaphase CheckpointSlide 44Cancer: Out-of-Control Cell DivisionTypes of Cancerous Cell DefectsProperties of Cancer CellsSlide 48Cancer Involves Loss of Cell-Cycle ControlSocial ControlSocial Controls and Cell-Cycle CheckpointsSlide 52Cancer Is a Family of DiseasesKey ConceptsSlide 55© 2011 Pearson Education, Inc.Chapter 11 – The Cell Cycle© 2011 Pearson Education, Inc.Introduction to Cell Division•Cells arise through the division of preexisting cells. There are two types of cell division: meiosis and mitosis.•Both forms of cell division are usually accompanied by cytokinesis, in which the cytoplasm of the cell divides into two distinct daughter cells.© 2011 Pearson Education, Inc.Contrasting Mitosis and Meiosis•Meiosis leads to the production of gametes (eggs and sperm).–Daughter cells have half the amount of genetic material as the parent cell.•Mitosis leads to the production of all other cell types, referred to as somatic cells.–Genetic material is copied and then divided equally.–Daughter cells are genetically identical to the parent cell.© 2011 Pearson Education, Inc.Functions of Mitosis•Mitosis and cytokinesis are responsible for three key events in multicellular eukaryotes:1. Growth2. Wound repair3. Asexual reproduction© 2011 Pearson Education, Inc.What Is a Chromosome?•Chromosomes contain a single long double helix of deoxyribonucleic acid (DNA) wrapped around proteins. –DNA encodes the cell’s genetic information. –A gene is a section of DNA that encodes a specific protein or RNA.•Chromosomes can be stained with dyes and observed under the light microscope.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.Chromosomes Change before and during Mitosis•The purpose of mitosis is to distribute chromosomes to daughter cells during cell division.–To this end, each chromosome is replicated prior to mitosis.•As mitosis starts, the chromosomes condense from long, thin filaments into compact structures that can be moved around the cell efficiently.•At the end of mitosis, one of the chromosome copies is distributed to each of two daughter cells.© 2011 Pearson Education, Inc.Chromosome Replication•Prior to mitosis, each chromosome is replicated. –Each of the DNA copies in a replicated chromosome is called a chromatid.–Chromatids are joined together along their entire length as well as at a specialized region of the chromosome called the centromere.–Chromatids from the same chromosome are referred to as sister chromatids.•Even though a replicated chromosome consists of two chromatids, it is still considered a single chromosome.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.M Phase and Interphase•Growing cells cycle between a dividing phase called the mitotic (M) phase and a nondividing phase called interphase.© 2011 Pearson Education, Inc.Interphase – S Phase•The cell cycle is the orderly sequence of events that occurs from the formation of a eukaryotic cell through the duplication of its chromosomes to the time it undergoes cell division.•A visualization technique called autoradiography allowed researchers to identify the part of the cell cycle during which DNA replication occurs.•Chromosome replication occurs only during interphase and not during M phase. –The stage in which DNA replication occurs is called the synthesis (S) phase.© 2011 Pearson Education, Inc.Interphase – Gap Phases•Interphase also includes two gap phases, during which no DNA synthesis occurs. –The first gap, G1 phase, occurs before the S phase. –The second gap, G2 phase, occurs between S phase and mitosis.•During the gap phases, organelles replicate and additional cytoplasm is made in preparation for cell division.•It takes a cell about 24 hours to complete one cell cycle. –G1 phase lasts 7–9 hours.–S phase lasts 6–8 hours.–G2 phase lasts 4–5 hours.© 2011 Pearson Education, Inc.The Cell CycleThere are a total of four phases in the cell cycle: M phase and an interphase consisting of the G1, S, and G2 phases.•Gap phases allow the cell to grow large enough and synthesize enough organelles to ensure the daughter cells will be normal in size and function.© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.Mitosis Overview•Mitosis results in the division of replicated chromosomes and formation of two daughter nuclei with identical chromosomes and genes.–Mitosis is usually accompanied by cytokinesis.•Every species has a characteristic number of chromosomes.–Humans have 46.© 2011 Pearson Education, Inc.Chromosomes Change during the Cell Cycle•Eukaryotic chromosomes consist of DNA associated with histone proteins. –In eukaryotes this DNA-protein material is called chromatin.•During interphase, most chromatin is “relaxed” or uncondensed, forming long, threadlike strands.•After replication during S phase, each chromosome consists of two genetically identical sister chromatids attached at the centromere.•At the start of mitosis the replicated chromosomes condense.© 2011 Pearson Education, Inc.Events in MitosisDuring mitosis, the two sister chromatids separate to form independent chromosomes, and one copy of each chromosome goes to each of the two daughter cells. As a result, each daughter cell receives a copy of the genetic information that is contained in each chromosome.•Mitosis (M phase) is a continuous process with five subphases based on specific events: –Prophase–Prometaphase–Metaphase–Anaphase–Telophase© 2011 Pearson Education, Inc.© 2011 Pearson Education, Inc.Prophase •During prophase, chromosomes condense and first become visible in the light


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UT Knoxville BIOL 140 - Chapter 11

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