Question:
Which one of the following experiments by Griffith with Streptococcus pneumoniae, resulted in the death of mice due to pneumonia?
Which one of the following experiments by Griffith with Streptococcus pneumoniae, resulted in the death of mice due to pneumonia?
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Only live bacteria can cause disease, and live R cells were transformed by heat-killed S cells.
Updated On: Nov 12, 2026
- Mice injected only with heat killed S strain.
- Mice injected with live R strain and heat killed S strain.
- Mice injected with heat killed R as well as S strains.
- Mice injected only with heat killed R strain.
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The Correct Option is B
Solution and Explanation
Step 1: Understanding the Concept
In Griffith's experiment, S strain (capsulated) is virulent and R strain (no capsule) is harmless.
Step 2: Check each injection
Heat-killed S alone, killed R alone, or both killed together have no living cells, so the mice survive.
Step 3: The transforming mix
Live R plus heat-killed S: some R cells take up the transforming principle from S, become S type and kill the mice.
Final Answer:
Mice died after injection with live R strain and heat-killed S strain. \[ \boxed{\text{(B) }\text{Mice injected with live R strain and heat killed S strain.}} \]
In Griffith's experiment, S strain (capsulated) is virulent and R strain (no capsule) is harmless.
Step 2: Check each injection
Heat-killed S alone, killed R alone, or both killed together have no living cells, so the mice survive.
Step 3: The transforming mix
Live R plus heat-killed S: some R cells take up the transforming principle from S, become S type and kill the mice.
Final Answer:
Mice died after injection with live R strain and heat-killed S strain. \[ \boxed{\text{(B) }\text{Mice injected with live R strain and heat killed S strain.}} \]
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