Assertion : In Griffith's experiment, a mixture of heatkilled virulent bacteria R strain and live no

Question

Assertion : In Griffith's experiment, a mixture of heatkilled virulent bacteria R strain and live non-virulent bacteria $S$ strain, lead to the death of mice.\ Reason : Some 'transforming principle' is transferred from heat-killed $S$ strain to $R$ strain and made it virulent.\

Professor PC Thomas Classes · Answer

(d) : When bacteria Streptococcus pneumoniae 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. In Griffith's experiment, some 'transforming principle', transferred from the heat-killed $S$ strain, had enabled the $R$ strain to synthesise a smooth polysaccharide coat and become virulent which must be due to the transfer of the genetic material. This is known as transformation.