( ( The chromosomes ) ( ( are ( pulled ( by ( spindle fibers ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NNS chromosomes)) (VP (VBP are) (VP (VBN pulled) (PP (IN by) (NP (JJ spindle) (NNS fibers))))) (. .)))
The chromosomes are pulled by spindle fibers.
(ROOT (S (NP (JJ Spindle) (NNS fibers)) (VP (VBP pull) (NP (VBN linked) (NNS chromosomes)) (PP (ADVP (RB apart)) (IN in) (NP (JJ anaphase) (NN i.))))))