Frederick Griffith's Experiment.ppt GENx

PPT GENETICS

1. Frederick Griffith's Experiment By Group 1: Flora Mae Morala Nicole Daquis Andre Nicole Salutan Kiara Mae Bangi John Vincent Ajoc John Patrick Ybañez Ian Ibañez

2. FREDERICK GRIFFITH 2 British bacteriologist ( born October 3, 1877, Eccleston, Lancashire, England—died 1941, London) Performed an experiment on Bacterium Streptococcus pneumoniae (causative agents of pneumococcal infection) 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. 2/22/2024

3. FREDERICK GRIFFITH He was studying Pathogenicity of different strains of bacteria- Diplococcus Pneumoniae  *He studied the effect of two different strains of bacteria.  “R” Strain -rough colonies devoid of mucilaginous sheath - non virulent (non-infectious) “S” Strain -form smooth colonies having mucilaginous sheath - virulent (strongly infectious)

4. FREDERICK GRIFFITH 1) R strain Injected in mice- mice survived 2) S strain Injected in mice- mice died   3) Heat killed S strain Injected in mice- mice survived   4) Heat killed S strain + R strain Injected in mice- mice died

5. Griffith’s Conclusion • Based on the observation, Griffith concluded that R strain bacteria had been transformed by the heat-killed S strain bacteria. • The R strain inherited some 'transforming principle' from the heat- killed S strain bacteria and had enabled the R-strain to synthesize a smooth polysaccharide coat which made them virulent. • He assumed this transforming principle as genetic material.

6. DNA and Genetic material • Griffith's experiment was a turning point towards the discovery of hereditary material. • However, it failed to explain the biochemistry of genetic material. • Hence, a group of scientists, Oswald Avery, Colin MacLeod and Maclyn McCarty continued the Griffith experiment in search of biochemical nature of the hereditary material. • Their discovery revised the concept of protein as genetic material to DNA.

7. Avery, MacLeod and McCarty's conclusion • They repeated Griffith’s Experiment on 1944 • They extracted and purified proteins, DNA, RNA and other biomolecules from the heat-killed S strain bacteria. • They discovered that DNA is the genetic material and it is alone responsible for the transformation of the R strain bacteria.

8. Avery, MacLeod and McCarty's conclusion • They observed that protein-digesting enzymes (proteases) and RNA- digesting enzymes (RNases) didn't inhibit transformation but DNase did. • Although it was not accepted by all, they concluded DNA as genetic material.