Paragraph 1：The history of biology is filled with incidents in which research on one specific topic has contributed richly to another, apparently unrelated area. Such a case is the work of Frederick Griffith, an English physician whose attempts to prevent the disease pneumonia led to the identification of the material in cells that contains genetic information, the information that determines an organism’s characteristic structure. In the 1920s, Griffith was studying the bacterium Streptococcus pneumoniae, or pneumococcus, one of the organisms that cause pneumonia in humans. He was trying to develop a vaccine against this devastating illness. He was working with two strains of the bacteria pneumococcus. A bacterial strain is a population of cells descended from a single parent cell; strains differ in one or more inherited characteristics. Griffith’s strains were designated S and R because, when grown in the laboratory, one produced shiny, smooth (S) colonies or groups of bacteria, and the other produced colonies that look rough (R).
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