( explain ( ( the role ) ( of ( ( sperm ( and ( egg cells ) ) ) ( in ( sexual reproduction ) ) ) ) ) )
(ROOT (S (VP (VB explain) (NP (NP (DT the) (NN role)) (PP (IN of) (NP (NP (NN sperm) (CC and) (NN egg) (NNS cells)) (PP (IN in) (NP (JJ sexual) (NN reproduction)))))))))
explain the role      of sperm and egg cells in sexual reproduction
(ROOT (S (NP (NP (JJ Sexual) (NN reproduction)) (, ,) (PP (IN in) (NP (NN general))) (, ,)) (VP (VBZ relies) (PP (IN on) (NP (NP (NNS sets)) (PP (IN of) (NP (NP (NNS cells)) (SBAR (WHNP (WDT that)) (S (VP (VBP are) (NP (NP (NNS precursors)) (PP (IN for) (NP (NNS eggs) (CC and) (NN sperm)))))))))))) (. .)))