GRIFFITH’S EXPERIMENT

1. GRIFFITH’S EXPERIMENT INTRODUCTION Griffith's experiments (1928) first demonstrated that genetic information could be transferred. Without knowing what this information was, he called it the "Transforming Principle". It was the first step towards Proving that Nucleic Acids and not the Proteins are the chemical basis of experiment

2. *He was studying Pathogenicity of different strains of bacteria-Diplococcus Pneumoniae *He studied the effect of two different strains of bacteria. R-II Type-irregular ,rough colonies devoid of mucilaginous sheath - non Virulent S-III Type-form smooth colonies having mucilaginous sheath -Virulent.

3. EXPERIMENT Test animal - Mice R II type Injected in mice mice survived S III type Injected in mice mice died Heat killed S type Injected in mice mice survived Heat killed S type + R II type Injected in mice mice died

4. PICTORIALVIEW

8. OBSERVATION & CONCLUSION Fourth part of experiment was a great surprise for him. 1 .When Griffiths co-injecting a mixture of heat-killed virulent bacteria (which could not cause pneumonia) and living avirulent bacteria (which also could not cause pneumonia) he found that the injected mice would contract Pneumonia and die. 2 .When he isolated bacteria from the blood of the of the dead mouse, he found living VIRULENT bacteria.

9. 3 . Griffiths interpreted this to indicate that ome substance (the Transforming Principle) had been transferred from the dead bacteria to the living avirulent strain, "transforming" this strain into the virulent strain. 4. He concluded R II type bacteria had been transformed into S III type – Transformation.

10. How would you design an experiment to prove that DNA was responsible for transformation? Griffith’s Experiment did not prove that DNA was responsible for transformation

11. Avery, McCarty, and MacLeodRepeated Griffith’s Experiment Oswald Avery Maclyn McCarty Colin MacLeod

12. Avery, McCarty, and MacLeodAdded the non-deadly Rough Type of Bacteria to the Heat-Killed Smooth Type To the Heat-Killed Smooth Type, added enzymes that destroyed… Carbohydrates Lipids Proteins RNA DNA

13. S-Type Carbohydrates Destroyed S-Type Lipids Destroyed S-Type Proteins Destroyed S-Type RNA Destroyed S-Type DNA Destroyed Conclusion: DNA was the transforming factor!

14. Q1. Write the scientific name of the causative organism of pneumonia. Q2. What is meant by R-cells and S-cells with which Frederick Griffith carried out his experiments on Diplococcus pneumoniae? What did he prove from these experiments. HOMEWORK