Question

Describe the experiment performed by Griffith. What conclusions did he infer from his conclusions?

Answer 1

Hint: In 1928, Griffith's experiment accounted for the earliest experiment suggesting that bacteria are able to transfer genetic information by a process called transformation. Griffith's findings were followed by research in the late 1930s and early 40s that isolated DNA as the material that corresponds to this genetic information.

Complete answer:
The bacterium Diplococcus pneumoniae roots pneumonia in humans. One strain known as smooth types (S) has polysaccharide forming a big capsule around the cell. The other strain bacterial cells do not include the polysaccharide layer and the colony formed by these cells has an uneven appearance and is called the rough type (R). The S-strain is lethal while the R-strain is non-lethal.
In these experiments, Griffith inserted mice with liveR-type of bacteria. They did not suffer from the disease. When he inserted 'S'-a type of bacteria, the mice died. However, when heat-killed S-type bacteria were injected, they did not experience pneumonia. Then he injected the mice with a combination of live R-type with heat-killed S-type bacteria the mice died.

Griffith scrutinized that in the blood of dead mice, both R and S types of bacteria were there. He, therefore, concluded that heat-killed smooth-type bacteria responsible for a transformation of the living rough type bacteria. This experiment proposed that DNA and not proteins are genetic material.

Note:
We recognize that the "transforming principle" Griffith concluded was the DNA of the S strain bacteria. While the bacteria had been killed, the DNA had endured the heating process and was taken up by the R strain bacteria. The S strain DNA encloses the genes that form the smooth protective polysaccharide capsule. The correct nature of the transforming principle was confirmed by Avery, McLeod, and McCarty and by Hershey and Chase.