1 Griffith’s Experiments In 1928, British medical officer Frederick Griffith was studying a bacterium called Streptococcus Pneumoniae (S. Pneumoniae) . Some types or strains of this bacterium can cause the lung disease PNEUMONIA in mammals. Griffith was trying to develop a vaccine against a disease-causing or VIRULENT strain of bacterium. As shown in the picture below, each virulent bacterium is surrounded by a capsule made of polysaccharides that protects it from a body’s defense system. The bacteria in a virulent strain grow smooth-edged colonies when grown in a petri dish and are called the In contrast, S strain. a second strain of S. pneumonia does not cause pneumonia and lacks a capsule. The second strain is called the R strain because it grows into rough colonies. 1. What is a virulent? 2. What are virulent bacterium capsules made of? 3. What type of edges did the colonies of the S strain possess? 2 Griffith’s Mice Griffith used the two (2) strains of S. pneumoniae bacteria in a series of four (4) experiments. In experiments 1 and 2, Griffith injected either live R or live S strain cells into mice. He found that only S strain cells killed mice. In experiment 3, he injected heat-killed S strain bacteria into mice and found that the mice survived. In his fourth experiment, he injected mice with both heat-killed S strain cells & live R strain cells and found that the mice died. Griffith concluded from his four (4) experiments that heat-killed virulent bacterial cells release a hereditary factor that transfers the disease-causing ability to live harmless cells. This type of transfer of genetic material form one cell to another cell or from one organism to another organism is called TRANSFORMATION. 1. What strain cells killed mice? 2. What is a transformation?
1 Griffith’s Experiments In 1928, British medical officer Frederick Griffith was studying a bacterium called Streptococcus Pneumoniae (S. Pneumoniae) . Some types or strains of this bacterium can cause the lung disease PNEUMONIA in mammals. Griffith was trying to develop a vaccine against a disease-causing or VIRULENT strain of bacterium. As shown in the picture below, each virulent bacterium is surrounded by a capsule made of polysaccharides that protects it from a body’s defense system. The bacteria in a virulent strain grow smooth-edged colonies when grown in a petri dish and are called the S strain. In contrast, a second strain of S. pneumonia does not cause pneumonia and lacks a capsule. The second strain is called the R strain because it grows into rough colonies. 1. What is a virulent? 2. What are virulent bacterium capsules made of? 3. What type of edges did the colonies of the S strain possess? 2 Griffith’s Mice Griffith used the two (2) strains of S. pneumoniae bacteria in a series of four (4) experiments. In experiments 1 and 2, Griffith injected either live R or live S strain cells into mice. He found that only S strain cells killed mice. In experiment 3, he injected heat-killed S strain bacteria into mice and found that the mice survived. In his fourth experiment, he injected mice with both heat-killed S strain cells & live R strain cells and found that the mice died. Griffith concluded from his four (4) experiments that heat-killed virulent bacterial cells release a hereditary factor that transfers the disease-causing ability to live harmless cells. This type of transfer of genetic material form one cell to another cell or from one organism to another organism is called TRANSFORMATION. 1. What strain cells killed mice? 2. What is a transformation?
DNA-RNA-Protein-Synthesis-stations.docx