"Nucleic acids must be regarded as possessing biological specificity the chemical basis of which is as yet undetermined" -Oswald Avery
"The evidence presented supports the belief that a nucleic acid of the deoxyribose type is the fundamental unit of the transforming principle of Pneumococcus Type III." (Avery, MacLeod, & McCarty)
http://jem.rupress.org/content/suppl/2004/01/30/199.3.DC1/1.pdf
"The evidence presented supports the belief that a nucleic acid of the deoxyribose type is the fundamental unit of the transforming principle of Pneumococcus Type III." (Avery, MacLeod, & McCarty)
http://jem.rupress.org/content/suppl/2004/01/30/199.3.DC1/1.pdf
This was a very controlled experiment. Avery, MacLeod, and McCarty tested several different variables, like the sugar coating, proteins, RNA, and DNA. To prevent error, they took an original product and extracted one component at a time. For example, first they eliminated the sugar coating from the cells, then they tested the ability of the new product to transform. When they found that it could transform, they moved on to eliminating a different component and tested that. This process of elimination is necessary to a quality experiment because it allows multiple variables to be tested, but only one variable at a time.