( ( In ( a ( diploid cell ) ) ) ( , ( chromosomes ( ( occur ( as pairs ) ) . ) ) ) )
(ROOT (S (PP (IN In) (NP (DT a) (JJ diploid) (NN cell))) (, ,) (NP (NNS chromosomes)) (VP (VBP occur) (PP (IN as) (NP (NNS pairs)))) (. .)))
In a diploid cell, chromosomes occur as pairs.
(ROOT (S (NP (EX There)) (VP (VBP are) (NP (NP (CD 46) (NNS chromosomes) (NNS chromosomes)) (PP (IN in) (NP (DT a) (JJ diploid) (JJ human) (NN cell))))) (. .)))