Chapter 11 - BSC 1010 Dr. Presley Chapter 11 THE GENETIC...

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BSC 1010 Dr. Presley Chapter 11 THE GENETIC MATERIAL CHARACTERISTICS of the genetic material : -stores information -can be replicated -relatively stable (undergoes few changes) -located in nucleus and chromosomes **large information database requires large molecule ***Early considerations: The genetic material is either protein or DNA THE SEARCH FOR THE GENETIC MATERIAL: Since a large molecule in the nucleus was likely to be the genetic material, the problem was to determine if the genetic material was protein or DNA. -CHEMICAL DISCOVERY Miescher 1869 isolated nuclein from nuclei of pus, phosphorous-rich material later purified as gummy, acidic = nucleic acid now known as DNA and RNA -BIOCHEMISTS - 1900's reveal clues to genetic control of enzymatic pathways ignored because of interest in counting results of genetic crosses - Griffith’s Experiment - 1928 Study Figure 11.1 on page 214 ** Know this, we will revisit it in later chapters Transformation of bacteria - first type of Streptococcus pneumoniae was the S strain with shiny, smooth colonies. Bacteria have capsule to protect against host defenses. When injected into mouse, the mouse died as the result of this virulent strain. - second type of pneumonia bacterium was the R strain with rough colonies lacking a capsule. When injected into the mouse, the mouse lived. This strain is considered non-virulent . - after heat killing, the S strain was injected into the mouse and the mouse lived. - next the heat-killed S strain and the non-virulent R strain were mixed and this mixture was injected into the mouse. The result was that the mouse died. - using basic microbial processing as outlined by Koch’s postulates (text p. 532), it was discovered that the isolated living bacteria from the dead mouse was a virulent S strain of the pneumonia. What had transformed the living non-virulent R strain in the mixture to the virulent S strain? Remember only dead S strain bacteria were in the mixture. - something had been taken up by the living bacteria and transformed them into the virulent S strain. - Since heat will denature proteins, this experiment cast doubt that the genetic transforming principle was nuclear proteins. - Avery, McCarty, MacLoud 1944 Therefore DNA could be the transforming principle - “Blender Experiment” - 1952 Study Figure 11.3 on page 216 ** Know this, we will revisit it in later chapter Used a bacteriophage (virus or phage) – Study Fig 11.2 on page 215 Observe the structure: protein coat, nucleic acid core The perfect tool to settle the protein or DNA argument Note that they infect bacteria, take over the metabolic machinery of the host cell for the production of new virus. Certainly transforming the infected cell into viral activity. T-2 bacteriophage
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This note was uploaded on 03/31/2008 for the course BIOL 1010 taught by Professor Staff during the Spring '06 term at Virginia Tech.

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Chapter 11 - BSC 1010 Dr. Presley Chapter 11 THE GENETIC...

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