( ( Genetic code ) ( ( was ( discovered ( ( some tens ) ( of ( years letter ) ) ) ) ) . ) )
(ROOT (S (NP (JJ Genetic) (NN code)) (VP (VBD was) (VP (VBN discovered) (NP (NP (DT some) (NNS tens)) (PP (IN of) (NP (NNS years) (NN letter)))))) (. .)))
Genetic code was discovered some tens of years letter.
(ROOT (S (NP (DT The) (JJ genetic) (NN code)) (VP (VBZ works) (PP (IN in) (NP (NP (NN series)) (PP (IN of) (NP (JJ three-letter) (NNS codes)))))) (. .)))