( It ( ( ( ( ( took years ) ( to ( determine ( ( the ( ( three billion ) letters ) ) ( of ( the ( human ( genetic code ) ) ) ) ) ) ) ) , ) ( though ( ( the job ) ( might ( be ( ( done ( in months ) ) now ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP It)) (VP (VBD took) (NP (NNS years)) (S (VP (TO to) (VP (VB determine) (NP (NP (DT the) (QP (CD three) (CD billion)) (NNS letters)) (PP (IN of) (NP (DT the) (JJ human) (JJ genetic) (NN code))))))) (, ,) (SBAR (IN though) (S (NP (DT the) (NN job)) (VP (MD might) (VP (VB be) (VP (VBN done) (PP (IN in) (NP (NNS months))) (ADVP (RB now)))))))) (. .)))
It took years to determine the three billion letters of the human genetic code, though the job might be done in months now.
(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)))))) (. .)))