AP BIOLOGY

Detailed explanation-1: -However, the most definitive proof that the transforming principle was DNA was its sensitivity to specific enzymes, called DNAses, that specifically degrade different kinds of DNA. Avery and his colleagues were able to show that transforming activity was not destroyed by enzymes that degrade proteins or RNA.

Detailed explanation-2: -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.

Detailed explanation-3: -Enter Oswald Avery and his colleagues. Working in test tubes, they used detergent to break open the heat-killed S cells to separate out the different components: They then destroyed the components one by one to identify which component was the ‘transforming principle’. The team” published their results in 1944.

Detailed explanation-4: -Avery and McCarty observed that proteases-enzymes that degrade proteins-did not destroy the transforming principle. Neither did lipases-enzymes that digest lipids. They found that the transforming substance was rich in nucleic acids, but Ribonuclease, which digests RNA, did not inactivate the substance.