The two main differences between RNA and DNA are

Explanation

They conducted experiment on T2-phage, a parasite on bacterium E. coli and prepared two types of `T_(2)-phages`:
(a) One containing radioactive sulphur and
(b) Other radioactive phosphorus. These were made to infect normal bacteria in two separate samples. After infection the bacterial cells ruptured liberating daugther phages. By the test for radioactivity it was found that radioactive phosphorus was passed on to the daughter phages while radioactive sulphur was found in the protein coat left outside the bacterial cell.