Griffith's Transformation Experiment — NEET Biology
📚 Practice ConceptWhen Streptococcus pneumoniae (pneumococcus) bacteria are grown on a culture plate, some produce smooth shiny colonies (S) while others produce rough colonies (R). This is because the S strain bacteria have a mucous (polysaccharide) coat, while R strain does not. Mice infected with the S strain (virulent) die from pneumonia infection but mice infected with the R strain do not develop pneumonia.
Which of the following statements are correct regarding the outcomes and implications of Frederick Griffith’s transforming principle experiment? S1. Mice injected with live S strain bacteria developed pneumonia and died. S2. Mice injected with live R strain bacteria did not develop pneumonia and survived. S3. Heat-killed S strain bacteria, when injected alone, caused pneumonia and death in mice. S4. When a mixture of heat-killed S strain and live R strain bacteria was injected, the mice died. S5. Griffith recovered living S strain bacteria from the dead mice in the experiment involving the mixture of heat-killed S and live R strains. S6. The experiment conclusively identified DNA as the chemical basis of the transforming principle.
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Correct answer: B — S1, S2, S4 and S5 are correct
Griffith's experiment demonstrated the phenomenon of transformation. Let's evaluate each statement: S1. Mice infected with the S strain (virulent) die from pneumonia infection. This statement is correct. S2. Mice infected with the R strain do not develop pneumonia. This statement is correct. S3. He observed that heat-killed S strain bacteria injected into mice did not kill them. So, this statement is incorrect. S4. When he injected a mixture of heat-killed S and live R bacteria, the mice died. This statement is correct. S5. Moreover, he recovered living S bacteria from the dead mice in the mixture experiment. This statement is correct. S6. The biochemical nature of genetic material was not defined from his experiments. So, this statement is incorrect. Therefore, statements S1, S2, S4, and S5 are correct.
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