( They ( ( ( used ( ( polymerase ( chain reaction ) ) ( -LRB- ( PCR -RRB- ) ) ) ) ( to ( ( create ( ( many copies ) ( of ( the ( HA ( and ( NA genes ) ) ) ) ) ) ) ( so ( they ( could ( look ( at them ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBD used) (NP (NP (NN polymerase) (NN chain) (NN reaction)) (PRN (-LRB- -LRB-) (NP (NNP PCR)) (-RRB- -RRB-))) (S (VP (TO to) (VP (VB create) (NP (NP (JJ many) (NNS copies)) (PP (IN of) (NP (DT the) (NNP HA) (CC and) (NNP NA) (NNS genes)))) (SBAR (IN so) (S (NP (PRP they)) (VP (MD could) (VP (VB look) (PP (IN at) (NP (PRP them))))))))))) (. .)))
They used polymerase chain reaction (PCR) to create many copies of the HA and NA genes so they could look at them.
(ROOT (S (NP (DT The) (NN polymerase) (NN chain) (NN reaction)) (VP (VBZ is) (NP (NP (DT a) (NN way)) (PP (IN of) (S (VP (VBG making) (NP (NP (NNS copies)) (PP (IN of) (NP (DT a) (NN gene))))))))) (. .)))