What did Avery's theory provide evidence for?
Ostwald T. Avery's experiment was an extension of the works of
Griffith's. Griffith's experiment using virulent and avirulent
Streptococcus pneumoniae (which had different colony
characteristics) proved that it was possible for the heat killed
virulent Streptococcus pneumoniae to pass on the genetic
information for formation of smooth colonies to avirulent strains.
Avery, Mc Leod and Mc Carty conclusively found out that the genetic
material responsible for transfer of characteristics between the
strains was DNA. This was achieved by incubating the cell lysate of
virulent Streptococcus with proteases, RNAses and DNAses separately
before mixing it with avirulent strains. It was found that only
when the lysate was incubated with DNAses did the transfer of
smooth colony formation characteristic from the virulent strain to
the avirulent strain fail to occur.