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. 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.
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.