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Lecture Biology (6e): Chapter 18 - Campbell, Reece

Chapter 18 - Microbial models: The genetics of viruses and bacteria. This chapter presents the following content: Researchers discovered viruses by studying a plant disease, a virus is a genome enclosed in a protective coat, viruses can only reproduce within a host cell, phages reproduce using lytic or lysogenic cycles,. | CHAPTER 18 MICROBIAL MODELS: THE GENETICS OF VIRUSES AND BACTERIA Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Section A: The Genetics of Viruses 1. Researchers discovered viruses by studying a plant disease 2. A virus is a genome enclosed in a protective coat 3. Viruses can only reproduce within a host cell: an overview 4. Phages reproduce using lytic or lysogenic cycles 5. Animal viruses are diverse in their modes of infection and replication 6. Plant viruses are serious agricultural pests 7. Viroids and prions are infectious agents even simpler than viruses. 8. Viruses may have evolved from other mobile genetic elements Viruses and bacteria are the simplest biological systems - microbial models where scientists find life’s fundamental molecular mechanisms in their most basic, accessible forms. Microbiologists provided most of the evidence that genes are made of DNA, and they worked out most of the major steps in DNA replication, transcription, and translation. Viruses and bacteria also have interesting, unique genetic features with implications for understanding diseases that they cause. Introduction Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Bacteria are prokaryotic organisms. Their cells are much smaller and more simply organized that those of eukaryotes, such as plants and animals. Viruses are smaller and simpler still, lacking the structure and most meta- bolic machinery in cells. Most viruses are little more than aggregates of nucleic acids and protein - genes in a protein coat. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 18.1 The story of how viruses were discovered begins in 1883 with research on the cause of tobacco mosaic disease by Adolf Mayer. This disease stunts the growth and mottles plant leaves. Mayer concluded that the disease was infectious when he found that he could transmit the disease by spraying sap from diseased leaves onto healthy plants. . | CHAPTER 18 MICROBIAL MODELS: THE GENETICS OF VIRUSES AND BACTERIA Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Section A: The Genetics of Viruses 1. Researchers discovered viruses by studying a plant disease 2. A virus is a genome enclosed in a protective coat 3. Viruses can only reproduce within a host cell: an overview 4. Phages reproduce using lytic or lysogenic cycles 5. Animal viruses are diverse in their modes of infection and replication 6. Plant viruses are serious agricultural pests 7. Viroids and prions are infectious agents even simpler than viruses. 8. Viruses may have evolved from other mobile genetic elements Viruses and bacteria are the simplest biological systems - microbial models where scientists find life’s fundamental molecular mechanisms in their most basic, accessible forms. Microbiologists provided most of the evidence that genes are made of DNA, and they worked out most of the major steps in DNA replication, transcription, and .