What is the genetic material

Griffth experiment:

some cellular chemical can change the inheritance of a living organism

Diplococcus pneumococci casuses pneumonia like disease in mouse

Heating live D. pneumococci kills bacteria and makes it nonvirulent

A nonvirulent (avirulent, rough) strain is D. pneumococci was isolated

Mice injected with avirulent strain of D. pneumococci did not die

Mice injected with heat killed (dead) virulent and live avirulent strains of D. pneumococci die.


Avery, MacCloud and Macarty chemically show that DNA is the genetic material

they used the S (virulent) and R (avirulent) strains of D. pneumococci

they chemically isolated and purified proteins, DNA, RNA, carbohydrates and lipids from the S strain

They treated the living avirulent R strain with each of these chemicals

only purified DNA changed the avirulent R starin into a virulent S strain

conclusion: DNA is the genetic material because it could change the genetic composition of a cell