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BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor CHAPTER 10 Molecular Biology of the Gene Virus Structure, Replication and the Body’s Defense Modules 10.17, 24.1-6 From PowerPoint® Lectures for Biology: Concepts & Connections Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings VIRUSES: GENES IN PACKAGES 10.17 Viral DNA may become part of the host chromosome Phage Attaches to cell Bacterial chromosome Phage DNA Cell lyses, releasing phages Phage injects DNA Many cell divisions Occasionally a prophage may leave the bacterial chromosome LYTIC CYCLE Phages assemble LYSOGENIC CYCLE Phage DNA circularizes Prophage Lysogenic bacterium reproduces normally, replicating the prophage at each cell division OR New phage DNA and proteins are synthesized Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Phage DNA inserts into the bacterial chromosome by recombination Click on Video links to Understand How Virus Replicate……. • Lambda Phage Viral Replication (test) • Replication of a Retrovirus (enrichment) • HIV Replication (enrichment) • HIV Replication Animation (enrichment) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 10.18 Connection: Many viruses cause disease in animals • Many viruses have RNA, rather than DNA, as their genetic material Membranous envelope RNA – Example: flu viruses Protein coat Glycoprotein spike Figure 10.18A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Glycoprotein spike VIRUS This slide is enrichment material • Some animal viruses steal a bit of the host cell’s membrane Protein coat Viral RNA (genome) Plasma membrane of host cell Envelope 1 Entry 2 Uncoating 3 RNA synthesis by viral enzyme Viral RNA (genome) 4 Protein synthesis 5 RNA synthesis (other strand) Template mRNA New viral proteins protein 6 New viral genome Assembly Exit 7 Figure 10.18B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 10.19 Connection: Plant viruses are serious agricultural pests • Most plant viruses have RNA – Example: tobacco mosaic disease Protein Figure 10.19 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings RNA 10.20 Connection: Emerging viruses threaten human health • The deadly Ebola virus causes hemorrhagic fever – Each virus is an enveloped thread of protein-coated RNA • Hantavirus is another enveloped RNA virus Figure 10.20A, B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 10.21 The AIDS virus makes DNA on an RNA template • HIV is a retrovirus: This is a good diagram to model virus parts Envelope Glycoprotein Protein coat RNA (two identical strands) Reverse transcriptase Figure 10.21A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings This is optional information if you are interested in retrovirus replication. You have knowledge to understand it. • Inside a cell, HIV uses its RNA as a template for making DNA to insert into the host chromosome Viral RNA CYTOPLASM 1 NUCLEUS DNA strand Chromosomal DNA 2 3 Doublestranded DNA Provirus DNA 4 5 RNA Viral RNA and proteins 6 Figure 10.21B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 10.22 Virus research and molecular genetics are intertwined • Virus studies help establish molecular genetics • Molecular genetics helps us understand viruses – such as HIV, seen here attacking a white blood cell Figure 10.22 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings NONSPECIFIC DEFENSES AGAINST INFECTION 24.1 Nonspecific defenses against infection include the skin and mucous membranes, phagocytic cells, and antimicrobial proteins • The body’s first lines of defense against infection are nonspecific – They do not distinguish one infectious microbe from another Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Macrophages wander in the interstitial fluid – They “eat” any bacteria and virus-infected cells they encounter Figure 24.1A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • Interferon and complement proteins are activated by infected cells Viral nucleic acid VIRUS 6 Antiviral proteins block 1 viral reproduction 2 Interferon New viruses genes turned on mRNA 5 Interferon 3 stimulates cell to turn on genes for antiviral proteins Interferon molecules HOST CELL 1 Makes interferon; is killed by virus Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 4 HOST CELL 2 Protected against virus by interferon from cell 1 Figure 24.1B 24.2 The inflammatory response mobilizes nonspecific defense forces • Tissue damage triggers the inflammatory response Skin surface Swelling Pin Phagocytes Bacteria Phagocytes and fluid move into area Chemical signals White blood cell 1 Tissue injury; release of chemical signals such as histamine 2 Dilation and increased leakiness 3 Phagocytes (macrophages and of local blood vessels; migration of phagocytes to the area neutrophils) consume bacteria and cell debris; tissue heals Figure 24.2 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings How Does the Body Defend Against Pathogens? Two Types of Defense Mechanisms: 1. Nonspecific Defense 2. Specific Defense Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • The inflammatory response can – disinfect tissues – limit further infection Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 24.10 Antibodies are the weapons of humoral immunity • An antibody molecule Figure 24.10A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings • An antibody molecule has antigen-binding sites specific to the antigenic determinants that elicited its secretion Antigen-binding sites Light chain Heavy chain Figure 24.10B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 24.11 Antibodies mark antigens for elimination • Antibodies may – block harmful antigens on microbes – clump bacteria or viruses together – precipitate dissolved antigens – activate complement proteins Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Binding of antibodies to antigens inactivates antigens by Neutralization (blocks viral binding sites; coats bacterial toxins) Agglutination of microbes Precipitation of dissolved antigens Complement molecule Bacteria Virus Antigen molecules Bacterium Enhances Phagocytosis Activation of complement Foreign cell Hole Leads to Cell lysis Macrophage Figure 24.11 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Lab: “What Happens When Holly Gets Sick?” • Holly Gets Sick Movie Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Click on the links to understand how the body fights pathogens: Good but may be a bit confusing. Study the Holly Gets Sick Video Questions • The Immune Response • Cytotoxic T Cell and the Target Cell Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings