Introduction:

• Experiment conducted by Frederick Griffith in 1928
• First experiment to demonstrate genetic material transfer between bacteria
• Laid foundation for discovery of DNA as genetic material and paved way for molecular biology

The Experiment:

• Involved two strains of Streptococcus pneumoniae bacteria: virulent (S) and non-virulent (R)
• Virulent strain caused pneumonia and had a smooth appearance due to polysaccharide capsule
• Non-virulent strain had a rough appearance

Steps of Experiment:

• Mice were injected with virulent strain and they died
• Mice were injected with a mixture of virulent and non-virulent strains and they did not die
• The non-virulent strain had transformed into the virulent strain
• Autopsy showed that the non-virulent bacteria had taken up the virulence factor (polysaccharide capsule) from the dead virulent bacteria
• Further experiments showed that a substance from the dead virulent bacteria (now called the transforming principle) was responsible for the transformation
• The transforming principle was later identified as DNA.

Conclusion:

• The experiment demonstrated that genetic material (DNA) could be transferred from one organism to another
• The experiment was a key step in the discovery of DNA as the genetic material
• The experiment paved the way for the development of molecular biology and genetic engineering.