Which of the following facts are correct regarding Frederick Griffith’s transforming principle?
A. Smooth colonies are produced because the S strain bacteria have a mucous coat.
B. Bacteria on culture plate result in some smooth colonies and some rough colonies.
C. Mice infected with the S strain of bacteria did not die from pneumonia infection.
D. Heat-killed S strain bacteria injected into mice and the mice were live.
Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → A, B and D only
In 1928 Frederick Griffith injected mice with two strains of Streptococcus pneumoniae. The S (smooth) strain has a mucous coat and causes pneumonia. The R (rough) strain has no coat and is harmless.
A. Smooth colonies are produced because the S strain bacteria have a mucous coat. — Correct. The mucous coat gives the S strain its smooth, shiny colonies.
B. Bacteria on culture plate result in some smooth colonies and some rough colonies. — Correct. S strain bacteria give smooth colonies and R strain bacteria give rough colonies. Both kinds were seen in the experiment.
C. Mice infected with the S strain of bacteria did not die from pneumonia infection. — Incorrect. Mice infected with live S strain bacteria died of pneumonia. Mice infected with the R strain did not.
D. Heat-killed S strain bacteria injected into mice and the mice were live. — Correct. Heat-killed S bacteria could not cause disease, so the mice lived.
NCERT Extract:
The Search for Genetic Material – “… When Streptococcus pneumoniae (pneumococcus) bacteria are grown on a culture plate, some produce smooth shiny colonies (S) while others produce rough colonies (R). This is because the S strain bacteria have a mucous (polysaccharide) coat, while R strain does not. Mice infected with the S strain (virulent) die from pneumonia infection but mice infected with the R strain do not develop pneumonia.”
The Search for Genetic Material – “… Griffith was able to kill bacteria by heating them. He observed that heat-killed S strain bacteria injected into mice did not kill them.”