( ( ( The ( basic unit ) ) ( of DNA ) ) ( ( is ( called ( ( ( a nucleotide ) , ) ( which ( is ( in ( turn ( composed ( of ( ( ( ( ( ( a sugar ) , ) ( a phosphate ) ) , ) and ) ( a ( nitrogen-containing base ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (JJ basic) (NN unit)) (PP (IN of) (NP (NNP DNA)))) (VP (VBZ is) (VP (VBN called) (NP (NP (DT a) (NN nucleotide)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBZ is) (PP (IN in) (NP (NP (NN turn)) (VP (VBN composed) (PP (IN of) (NP (NP (DT a) (NN sugar)) (, ,) (NP (DT a) (NN phosphate)) (, ,) (CC and) (NP (DT a) (JJ nitrogen-containing) (NN base))))))))))))) (. .)))
The basic unit of DNA is called a nucleotide, which is in turn composed of a sugar, a phosphate, and a nitrogen-containing base.
(ROOT (S (NP (NP (DT The) (NN base)) (PP (IN of) (NP (NP (DT a) (NN nucleotide)) (PP (IN within) (NP (NN dna)))))) (VP (VBZ consists) (PP (IN of) (NP (NN nitrogen)))) (. .)))