Central Dogma

Definition of Gene

Proof that DNA
is Genetic Material

DNA Structure

Restriction Modification

Nucleic Acid

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Proof that DNA is Genetic Material


When he added dead, virulent pneumonia bacteria to a mouse, it lived; but if he added dead virulent bacteria to live non-virulent bacteria some mice died. He termed the material that changed the non-virulent bacteria to virulent the transforming principle.

Avery, MacLeod and McCarty

They used biochemical purification of cellular fractions to determine that DNA and not RNA or protein was the transforming principle.

Transformation - the alteration of phenotype by the addition of foreign DNA

Hershey and Chase The "Blender Experiment"

They knew that:
    DNA - has P but no S
    Protein - has S but not P
They also knew that something from T2 phage entered E. coli cells and directed the bacteria to produce more phage. They assumed that the genetic material was the material that entered the cell. So they set out to determine the chemical nature of the material. In separate experiments they infected E. coli cells with 35S or 32P labeled phage. By analyzing the products they determined that 32P entered the cell. Thus DNA must be the genetic material.

Copyright © 1998. Phillip McClean