Question

Which is incorrect with reference to the transforming principle?

• A. $S\text{strain}\left(\text{heat killed}\right)+\text{R strain(live)}\to \text{inject into mice}\to \text{mice live}$
• B. $S\text{strain}\left(\text{heat killed}\right)\to \text{Inject into mice}\to \text{Mice live}$
• C. $R\text{strain}\to \text{Inject into mice}\to \text{Mice live}$
• D. $S\text{strain}\to \text{Inject into mice}\to \text{Mice die}$

Answer 1

The correct option is A $S\text{strain}\left(\text{heat killed}\right)+\text{R strain(live)}\to \text{inject into mice}\to \text{mice live}$

Part 1: Option A
In Griffith’s experiment, the smooth (S) strain of Streptococcus pneumoniae was virulent and the rough (R) strain was non-virulent.
When the live S strain was injected into the mouse it died.
Thus, the statement in option A is correct.

Part 2: Option B
When the live R strain was injected it lived.
Thus, the statement in option B is correct.

Part 3: Option C
When the heat killed S strain alone injected into the mouse it lived. Thus, the statement in option C is correct.

Part 4: Option D
When the live R strain and heat killed S strain were injected together the mouse died. This is because the R strain has acquired some transforming principle from heat killed S strain and got transformed into a virulent strain.
Thus, the statement in option D is incorrect.

Final answer
(d)$S\text{strain}\left(\text{heat killed}\right)+\text{R strain(live)}\to \text{inject into mice}\to \text{mice live}$