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Key Figures to the discovery of the Double Helix.

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Presentation on theme: "Key Figures to the discovery of the Double Helix."— Presentation transcript:

1 Key Figures to the discovery of the Double Helix

2 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)

3 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

4 The Experiment  INSERT FARAH’S DIAGRAM

5 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.

6 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!

7 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

8 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

9 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.

10 Impact on the Science community  enabled others to point out that DNA was the molecule of inheritance

11 References  nphsscience.com/barra/classes/bio_h/handout _dna_scientist.doc  ml  d= AAl7c01

12 The End  Oh and by the way… he never did find the vaccine Done by: Deborah, Durkasri, Elaine, Farah, Feng Yue


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