( ( By 1997 ) ( , ( researchers ( ( ( ( ( took it ) ( ( a step ) further ) ) , ) ( zeroing ( in ( on ( ( ( a ( specific gene ) ) ( on ( chromosome 4 ) ) ) ( which ( codes ( for ( ( alpha-synuclein , ) ( a ( nervous ( system protein ) ) ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN By) (NP (CD 1997))) (, ,) (NP (NNS researchers)) (VP (VBD took) (NP (PRP it)) (ADVP (NP (DT a) (NN step)) (RBR further)) (, ,) (S (VP (VBG zeroing) (PP (IN in) (IN on) (NP (NP (DT a) (JJ specific) (NN gene)) (PP (IN on) (NP (NN chromosome) (CD 4))) (SBAR (WHNP (WDT which)) (S (VP (VBN codes) (PP (IN for) (NP (NP (NN alpha-synuclein)) (, ,) (NP (DT a) (JJ nervous) (NN system) (NN protein)))))))))))) (. .)))
By 1997, researchers took it a step further, zeroing in on a specific gene on chromosome 4 which codes for alpha-synuclein, a nervous system protein.
(ROOT (S (NP (NP (NNS Genes)) (, ,) (CC or) (NP (NP (JJ functional) (NNS units)) (PP (IN of) (NP (NNS chromosomes)))) (, ,)) (VP (VBP determine) (NP (JJ specific) (NNS characteristics)) (PP (IN by) (S (VP (VBG coding) (PP (IN for) (NP (JJ specific) (NNS proteins))))))) (. .)))