1. To establish the transforming principle as DNA, which enzymes were used by Avery et al?
I. DNAases                   II. RNAases 
III. Proteases               IV. Lipases
 

Avery etal isolated the biochemicals from heat killed S strain. These biochemicals were DNA, RNA and Protein. To establish which biochemical was responsible for converting R strain to S strain they used DNase, RNase and Protease and found no transformation of R strain to S strain when DNase was used which destroys DNA. When they used Proteases and RNase they found transformation.