( This ( ( is ( ( ( ( ( the phase ) ( ( in which ) ( DNA ( is replicated ) ) ) ) , ) thus ) ( ( the ( term ( S phase ) ) ) ( for ( synthesis ( of DNA ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This)) (VP (VBZ is) (NP (NP (NP (DT the) (NN phase)) (SBAR (WHPP (IN in) (WHNP (WDT which))) (S (NP (NNP DNA)) (VP (VBZ is) (VP (VBN replicated)))))) (, ,) (RB thus) (NP (NP (DT the) (NN term) (NNP S) (NN phase)) (PP (IN for) (NP (NP (NN synthesis)) (PP (IN of) (NP (NNP DNA)))))))) (. .)))
This is the phase in which DNA is replicated, thus the term S phase for synthesis of DNA.
(ROOT (S (PP (IN During) (NP (NP (DT the) (NN synthesis) (NN phase)) (PP (IN in) (NP (DT the) (NN cell) (NN cycle))))) (, ,) (NP (NN dna) (NN replication)) (VP (VBZ occurs)) (. .)))