( ( ( ( ( DNA ( always ( has ( ( two chains ) ( forming ( a ( double helix ) ) ) ) ) ) ) , ) and ) ( ( each chain ) ( is ( ( made up ) ( of nucleotides ) ) ) ) ) . )
(ROOT (S (S (NP (NNP DNA)) (ADVP (RB always)) (VP (VBZ has) (NP (NP (CD two) (NNS chains)) (VP (VBG forming) (NP (DT a) (JJ double) (NN helix)))))) (, ,) (CC and) (S (NP (DT each) (NN chain)) (VP (VBZ is) (VP (VBN made) (PRT (RP up)) (PP (IN of) (NP (NNS nucleotides)))))) (. .)))
DNA always has two chains forming a double helix, and each chain is made up of nucleotides.
(ROOT (S (NP (NNP Dna)) (VP (VBZ consists) (PP (IN of) (NP (NP (CD two) (JJ long) (NNS chains)) (PP (IN of) (NP (NNS nucleotides)))))) (. .)))