( ( These studies ) ( ( were ( ( undertaken ( at ( ( the time ) ( as ( the ( ( best available ) approach ) ) ) ) ) ) ( to ( ( nucleotide ( ( ( substitutions and ) small ) deletions ) ) ( in ( ( DNA , ) ( which ( comprise ( ( roughly one-third ) ( of ( ( the spectrum ) ( of ( ( radiation-induced damage ) ( in DNA ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT These) (NNS studies)) (VP (VBD were) (VP (VBN undertaken) (PP (IN at) (NP (NP (DT the) (NN time)) (PP (IN as) (NP (DT the) (ADJP (JJS best) (JJ available)) (NN approach))))) (S (VP (TO to) (VP (VB nucleotide) (NP (ADJP (JJ substitutions) (CC and) (JJ small)) (NNS deletions)) (PP (IN in) (NP (NP (NNP DNA)) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBP comprise) (NP (NP (QP (RB roughly) (NN one-third))) (PP (IN of) (NP (NP (DT the) (NN spectrum)) (PP (IN of) (NP (NP (JJ radiation-induced) (NN damage)) (PP (IN in) (NP (NNP DNA)))))))))))))))))) (. .)))
These studies were undertaken at the time as the best available approach to nucleotide substitutions and small deletions in DNA, which comprise roughly one-third of the spectrum of radiation-induced damage in DNA.
(ROOT (S (ADVP (RB Deletions)) (VP (VB remove) (NP (NP (QP (CD one) (CC or) (JJR more)) (NNS nucleotides)) (PP (IN from) (NP (DT the) (NN dna)))))))