Question

when experimenting with steptocuccus pneumoniae in the 1920 griffin included that some substance

biology

Answer 1

• Griffith try to study the bacteria responsible for a pneumonia
• This bacteria, a pneumococcus, occurred in two forms that differed in both appearance and infective properties.
• One form (S) was smooth and highly infective.
• The other form (R) was rough and harmless
• The S strain covers itself with a polysaccharide capsule that protects it from the host's immune system.
• This means that the host will die.
• The R strain does not have that protective shield around it and is killed by the host's immune system.

• Griffith also injected mice with S-strain bacteria that had been killed by heat.

• the killed bacteria did not harm the mice.

• when the dead S-strain bacteria were mixed with live R-strain bacteria and injected, the mice died.

• He said that something in the killed S strain was transferred to the previously harmless R strain, making the R strain deadly. He called this process transformation.

• He concluded that the R strain had been "transformed" into the lethal IS strain by a "transforming principle"

The experiments that actually revealed that DNA is the material responsible for transformation