Chapter 10 - Chapter 10 Lecture Outline Introduction...

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Chapter 10 Lecture Outline Introduction Saboteurs Inside Our Cells A. The chromosome theory of inheritance set the historical and structural stage for the development of a molecular understanding of the gene. B. Many of the basics of molecular biology began to be understood by studying viruses and the mechanism used by viruses to gain control over DNA replication and the transcriptional and translational machinery of a cell. 1. Review: Are viruses living things? Recall some of the characteristics of life that viruses do not exhibit, particularly cellular structure and metabolism (Module 1.1). 2. Viruses are composed of a protein coat and internal DNA (or RNA), and they depend on the metabolism of their host to make more viral particles (Figure 10.1C). 3. Viruses infect all living things. 4. Experimental systems using phages (bacterial viruses or bacteriophages) were a logical choice for early experiments on the molecular biology of the gene. Phages are simple, with simple genes infecting relatively simple and easily manipulated bacteria. C. This chapter focuses on the structure of DNA, how it is replicated, and the process of protein synthesis through transcription and translation. I. The Structure of the Genetic Material Module 10.1 Experiments showed that DNA is the genetic material. A. DNA is commonly referred to by grade-school children and routinely manipulated by scientists. The identification of the structure and function of DNA as the heritable material was, however, not an easy task. The debate at the turn of the 20th century was over what the material of heredity was, protein or DNA. B. In 1928, Griffith showed (using Strepcoccus pneumoniae R= harmless strain and S= pathogenic strain) that some substance (he did not know what) conveyed traits (pathogenicity) from heat-killed bacteria to living bacteria without the trait. C. Evidence gathered during the 1930s and 1940s showed it was DNA rather than protein (both complex macromolecules found in chromosomes) that was the genetic material. D. In 1952, Hershey and Chase, using a virus called T2, showed that it was the DNA in the virus that infected the bacterial cell. Viruses of this type are called bacteriophages ( phages for short). E. The structure of a T2 phage is very simple, consisting of a protein coat and a DNA core (Figure 10.1A). F. Hershey and Chase devised a simple experiment using T2 phage and demonstrated that the radioactive isotope of sulfur (found only in proteins) was not transferred into new viral particles, whereas the radioactive isotope of phosphorus (found only in DNA) was transferred (Figure 10.1B). G. The reproductive cycle (also known as the lytic cycle) of a T2 phage results in the production of multiple copies of the T2 phage and the death of the infected bacterial cell (Figure 10.1C). Module 10.2
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Chapter 10 - Chapter 10 Lecture Outline Introduction...

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