Presentation on theme: "Key Figures to the discovery of the Double Helix."— Presentation transcript:
Key Figures to the discovery of the Double Helix
Introduction In 1928 an army medical officer named Frederick Griffith was trying to find a vaccine against streptococcus pneumoniae (the bacteria that causes pneumonia, a lung disease)
Significance But instead made a breakthrough in the world of heredity! He performed the first experiment which suggested that protein was not the genetic material
The Experiment INSERT FARAH’S DIAGRAM
The Experiment He did four experiments in which he injected strands of bacteria into mice, one strand that was harmless (R) and one that was harmful (S). In his first experiment, he injected the live R bacteria cells into a group of mice and the mice lived. In his second experiment, he injected the live S bacteria cells into a group of mice and mice died.
The Experiment In his third experiment, he killed the harmful S cells with extreme heat, and then injected the dead S cells into a group of mice and the mice lived. In his last experiment, he added live R cell (which are harmless) to the already dead heat-killed S cells, and then injected it into a group of mice, but the mice died!
Results even though he had killed the S cells, he hadn’t destroyed their hereditary material, which was the one part that caused the disease! the harmless R cells had used the information from the hereditary material of the dead S cells and became harmful he called this hereditary transformation
Conclusions The Live R had been transformed into Live S by some “transforming factor” the genetic information in the heat-killed virulent bacteria survived the heating process and was somehow incorporated into the genetic material of the non-virulent strain to cause them to become virulent
Conclusion But Griffith knew that heat denatures protein, so he suggested that the genetic material must be something else. However, his results did not specifically point to DNA as a possibility.
Impact on the Science community enabled others to point out that DNA was the molecule of inheritance
References nphsscience.com/barra/classes/bio_h/handout _dna_scientist.doc ml d= AAl7c01
The End Oh and by the way… he never did find the vaccine Done by: Deborah, Durkasri, Elaine, Farah, Feng Yue