Question

Frederick Griffith accidentally discovered transformation while attempting to
develop a vaccine for pneumonia. He injected mice with samples from S-strain
(virulent) and/or R-strain (non-virulent) pneumococcal bacteria (Streptococcus
pneumoniae). Which of the following results is NOT consistent with Griffith's
experiments?

• A. Injected S-strain: Mouse dies
• B. Injected R-strain: Mouse lives
• C. Injected heat-killed S-strain: Mouse lives
• D. Injected mixture of heat-killed S-strain and live R strain: Mouse lives

Answer 1

The correct option is D Injected mixture of heat-killed S-strain and live R strain: Mouse lives

The result - ‘Injected mixture of heat-killed S-strain and live R-strain: Mouse lives’, is not consistent with Griffith's experiments.


The mouse died when the mouse was injected with a mixture of heat-killed S-strain and live R-strain. Based on this observation, Griffith concluded that some transforming principle (a chemical substance) from the heat-killed, smooth S-strain virulent bacteria had entered the living, rough R-strain non-virulent bacteria and transformed the latter into virulent S-strain bacteria which in turn led to the death of the mouse due to pneumonia infection.