(S (S (ADVP (RB Instead)) (COMMA ,) (S (NP (BASENP (NN three) (NNS genes)) (PP (IN of) (BASENP (DT the) (NN HIV) (NN virus)))) (VP (VBP have) (VP (VBN been) (VP (VBN introduced) (PP (IN into) (BASENP (DT the) (NN adenovirus)))))))) (PERIOD .))