EXPERIMENT GRIFFITH

5 Agu

Griffith’s experiment, conducted in 1928 by Frederick Griffith, was one of the first experiments suggesting that bacteria are capable of transferring genetic information through a process known as transformation. Griffith used two strains of Streptococcus pneumoniae (which infects mice), a type III-S (smooth) and type II-R (rough) strain. The III-S strain covers itself with a polysaccharide capsule that protects it from the host’s immune system, resulting in the death of the host, while the II-R strain doesn’t have that protective capsule and is defeated by the host’s immune system. A German bacteriologist, Fred Neufeld, had discovered the three pneumococcal types (Types I, II, and III) and discovered the Quellung reaction to identify them in vitro.[3] Until Griffith’s experiment, bacteriologists believed that the types were fixed and unchangeable, from one generation to another. In this experiment, bacteria from the III-S strain were killed by heat, and their remains were added to II-R strain bacteria. While neither alone harmed the mice, the combination was able to kill its host. Griffith was also able to isolate both live II-R and live III-S strains of pneumococcus from the blood of these dead mice. Griffith concluded that the type II-R had been “transformed” into the lethal III-S strain by a “transforming principle” that was somehow part of the dead III-S strain bacteria. Today, we know that the “transforming principle” Griffith observed was the DNA of the III-S strain bacteria. While the bacteria had been killed, the DNA had survived the heating process and was taken up by the II-R strain bacteria. The III-S strain DNA contains the genes that form the protective polysaccharide capsule. Equipped with this gene, the former II-R strain bacteria were now protected from the host’s immune system and could kill the host.

ANALYSIS

1. Stating a problem In this experiment Griffith choose a problem about transfer of genetic to determine whether the bacteria can transfer the genetic information.

2. Problem formulating What bacteria can transfer genetic information? Not described in this article a preliminary study and hipothesis of this research is so directly direct.

3. Method work Griffith working method to experiment directly from hidu creature that is a mouse with a strain of bacteria enter into the mouse is a mouse strain penginfeksily choose working methode.

4. Conclution Griffith conclude that the bacterial type II-R was tranformed into strain III-B by a principle of transformation that had somehow become part III-S strains of bacteria are dead.

5. Matching It was true that the bacteria move genetic information though a process called transformation.

6. Publication This experiment can be successfuly and published until Griffith become the famous scientist.

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