The Question is from neet-botany molecular-basis-of-inheritance the-search-of-genetic-material, and it was created by the author Mr. NARESH KUMAR K

Question

What did Griffith observe when he injected a mixture of heat-killed S strain and live R strain bacteria into mice?

Mr. NARESH KUMAR K · Accepted Answer

## CORE INFORMATION
✓ **Answer**: A
## CONCEPT FRAMEWORK
 **Primary Concept**: Griffith's experiment and transformation principle
 **Related Topics**: Bacterial genetics, DNA as genetic material, virulence factors
 **Prerequisites**: Understanding of bacterial strains (S and R), heat-killing, and the concept of transformation.
## SOLUTION PATHWAY
**Given Information**:
  Griffith injected a mixture of heat-killed S strain (virulent, smooth colony) and live R strain (non-virulent, rough colony) bacteria into mice.
  [Important conditions]: The heat-killed S strain alone did not kill the mice, and the live R strain alone did not kill the mice.
**Method & Steps**:
 1. Analyze the experimental setup: Griffith's experiment aimed to understand the transformation of bacterial traits.
  Reasoning: The heat-killed S strain possessed some factor that could transform the harmless R strain into a virulent form.
  Formula/Rule: N/A
 2. Consider the outcome: The mice injected with the mixture died.
  Working: This indicates that the live R strain acquired the virulence factor from the heat-killed S strain.
  Key Point: This experiment demonstrated the existence of a 'transforming principle,' later identified as DNA.
 3. Determine the bacterial type recovered: Live S strain bacteria were recovered from the dead mice.
  Result: The R strain bacteria had been transformed into virulent S strain bacteria.
  Verification: The result supports the conclusion that a transforming principle from the heat-killed S strain was responsible for the transformation.
 ## OPTION ANALYSIS
A ✓: The mice died, and live S strain bacteria were recovered. This is the correct observation of Griffith's experiment, demonstrating the transformation of R strain to S strain.
B :x: The mice survived. This is incorrect; the mice died in this experimental group.
C :x: The mice died, and live R strain bacteria were recovered. This is incorrect; live S strain bacteria were recovered.
D :x: The mice survived, and a new strain of bacteria was recovered. This is incorrect; the mice died, and the recovered strain was the virulent S strain.
 ## LEARNING AIDS
 **Common Mistakes**:
  1.Confusing the roles of S and R strains: Remembering that S strain is virulent and R strain is non-virulent is crucial.
  2.Misunderstanding the transformation principle: The key is that the heat-killed S strain transferred genetic material to the live R strain.
 **Quick Tips**:
  1.Remember the acronym 'S' for 'smooth' and 'virulent' and 'R' for 'rough' and 'non-virulent'.
  2.Visualize the experiment: Imagine the heat-killed S strain releasing its genetic material that is taken up by the R strain, transforming it into the virulent S strain.

Mr. NARESH KUMAR K · Answer

The correct Option is "The mice died, and live S strain bacteria were recovered."

Mr. NARESH KUMAR K · Answer

The mice survived.

Mr. NARESH KUMAR K · Answer

The mice died, and live R strain bacteria were recovered.

Mr. NARESH KUMAR K · Answer

The mice survived, and a new strain of bacteria was recovered.

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