NEET BIOLOGY

Detailed explanation-1: -Conclusion: Based on the observation, Griffith concluded that R strain bacteria had been transformed by S strain bacteria. The R strain inherited some ‘transforming principle’ from the heat-killed S strain bacteria which made them virulent. And he assumed this transforming principle as genetic material.

Detailed explanation-2: -In their experiments, Hershey and Chase showed that when bacteriophages, which are composed of DNA and protein, infect bacteria, their DNA enters the host bacterial cell, but most of their protein does not. Hershey and Chase and subsequent discoveries all served to prove that DNA is the hereditary material.

Detailed explanation-3: -Frederick Griffith, (born October 3, 1877, Eccleston, Lancashire, England-died 1941, London), British bacteriologist whose 1928 experiment with bacterium was the first to reveal the “transforming principle, ” which led to the discovery that DNA acts as the carrier of genetic information.

Detailed explanation-4: -In Griffith’s experiment, the virulent S. pneumoniae that has a smooth (S) capsule in its appearance was capable of causing lethal infections upon injection into mice (Fig. 1.1).

Detailed explanation-5: -Oswald Avery, Colin MacLeod, and Maclyn McCarty showed that DNA (not proteins) can transform the properties of cells, clarifying the chemical nature of genes. Avery, MacLeod and McCarty identified DNA as the “transforming principle” while studying Streptococcus pneumoniae, bacteria that can cause pneumonia.