When avery and his colleagues had obtained the transforming factor from the iiisiiis virulent cells, they treated the fraction with proteases, ribonuclease, and deoxyribonuclease, followed by the assay for retention or loss of transforming ability.

The mentioned question is not complete. The complete question is:

When Avery and his colleagues had obtained the transforming factor from the IIIS virulent cells, they treated the fraction with proteases, ribonuclease, and deoxyribonuclease, followed by the assay for retention or loss of transforming ability. What were the purpose and results of these experiments? What conclusions were drawn?

The objective of treating the extraction with RNAse, proteases, and DNAse was to purify the fraction by selectively withdrawing protein, RNA and DNA. So, that it could be determined that what is the exact macromolecule, which was converting the avirulent cells into virulent cells. This is due to the fact that after degrading the macromolecule with the precise enzyme the conversion rate should have declined to zero if it was essential for transformation.  

The outcomes of the Avery experiment had demonstrated that after the fraction was mixed with protease and RNAse the mixture was still possessing the tendency to convert the avirulent strain. However, when the DNAse was supplemented, the rate of transformation reduced, and there was no more transformation detected.  

It was concluded by Avery and his colleagues that the DNA was the macromolecule accountable for the process of transformation as when it was degraded with DNAse in the extract transformation got ceased.