Paul Zamecnik first developed the cell-free extract system, which Marshall Nirenberg adapted to decipher the genetic code. Paul Zamecnik and Mahlon Hoagland also isolated activated tRNA, the "adaptor" that shuttled amino acids to ribsomes for incorporation into new protein chains.
protein chains,free extracts,amino acids,mahlon,genetic code,incorporation,dna,marshall
Marshall Nirenberg and Heinrich Matthaei used poly-U mRNA in a cell-free system to make a polyphenylalanine protein chain. This showed that UUU must be the code that specifies the amino acid phenylalanine.