( DNA ( ( is ( described ( as ( ( a ( double helix ) ) ( formed ( of ( ( two ( ( ( complementary and ) antiparallel ) strands ) ) ( of ( deoxyribose nucleotides ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP DNA)) (VP (VBZ is) (VP (VBN described) (PP (IN as) (NP (NP (DT a) (JJ double) (NN helix)) (VP (VBN formed) (PP (IN of) (NP (NP (CD two) (ADJP (JJ complementary) (CC and) (JJ antiparallel)) (NNS strands)) (PP (IN of) (NP (JJ deoxyribose) (NNS nucleotides)))))))))) (. .)))
DNA is described as a double helix formed of two complementary and antiparallel strands of deoxyribose nucleotides.
(ROOT (S (NP (DT The) (JJ double) (NN helix) (NN dna) (NN shape)) (VP (VBZ forms) (SBAR (WHADVP (WRB when)) (S (NP (DT the) (CD two) (JJ nucleotide) (NNS chains)) (VP (VB wrap) (PRT (RP around)) (NP (DT the) (JJ same) (NNS axis)))))) (. .)))