( ( DNA segments ) ( ( ( are then ) ( exchanged ( between ( ( the ( homologous strands ) ) ( in ( ( a ( complicated process ) ) ( called ( crossing over ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NN DNA) (NNS segments)) (VP (VBP are) (ADVP (RB then)) (VP (VBN exchanged) (PP (IN between) (NP (NP (DT the) (JJ homologous) (NNS strands)) (PP (IN in) (NP (NP (DT a) (JJ complicated) (NN process)) (VP (VBN called) (S (VP (VBG crossing) (PRT (RP over))))))))))) (. .)))
DNA segments are then exchanged between the homologous strands in a complicated process called crossing over.
(ROOT (S (NP (NP (NNP Exchange)) (PP (IN of) (NP (NN dna) (NNS segments)))) (VP (VBZ happens) (PP (IN between) (NP (NP (JJ non-sister) (NNS chromatids)) (PP (IN of) (NP (NP (RB homologous) (NNS chromosomes)) (PP (IN during) (NP (NN crossing-over)))))))) (. .)))