MHT CET Medical202624 April 2026Evening ShiftBiologyMolecular Basis of InheritanceActual
The transforming principle in Griffith's experiment was detected _______.
Options
- AWhen heat killed S-strain of S. pneumoniae were mixed up with the R-strain.
- BWhen the live S-strain of S. pneumoniae were mixed up with the R-stain.
- CWhen live R-strain of S. pneumoniae were mixed up with the S-strain.
- DWhen heat killed R-strain of S. pneumoniae were mixed up with the S-strain.
Correct answer
A. When heat killed S-strain of S. pneumoniae were mixed up with the R-strain.
Step-by-step solution
In Griffith's experiment, the transforming principle was detected when heat-killed S-strain (virulent) bacteria were mixed with live R-strain (non-virulent) bacteria and injected into mice. The mice died of pneumonia, and live S-strain bacteria were recovered from their blood. This indicated that some 'transforming principle' from the heat-killed S-strain had transformed the live R-strain into the virulent S-strain. Answer: When heat killed S-strain of S. pneumoniae were mixed up with the R-strain.