Question

Which one of the following sequences is not correct in relation to the experiment conducted by Griffith on Streptococcus pneumoniae to prove DNA as the genetic material?

• A. Live S‐strain‐Injected to mice‐Mice die
• B. Live R‐strain‐Injected to mice‐Mice live
• C. S‐strain [heat killed]‐Injected to mice‐Mice die.
• D. S‐strain [heat killed] +R strain alive‐Injected to mice‐Mice die

Answer 1

Answer: (C)

To prove DNA as the genetic material, Griffith conducted an experiment on bacterium Streptococcus pneumoniae. This bacterium causes pneumonia in animals including man.
This experiment is called transformation experiment. There are two strains of Streptococcus.
Rough[R] strain of bacteria produces rough colonies on culture media. These are non virulent. The other strain produces smooth colonies on culture media. They are called Smooth[S] strain and they are virulent. Griffith conducted a series of experiments with Streptococcus on mice.
A) He injected type R strain into the mice. The mice did not die.
B) He injected the type S strain into the mice. The mice died of pneumonia.
C) He injected heat killed type R strain to the mice. The mice did not die.
D) When he injected the mixture of heat killed smooth bacteria(S strain) and living R strain of Streptococcus, the mice died as this process resulted in the transformation of Live R strain and converted R strain into S strain