( ( Once ( ( the ovum ) ( is fertilized ) ) ) ( , ( there ( ( are ( ( ( two pronuclei ) , ) ( one ( originating ( from ( ( ( the ovum ) , ) ( the ( ( other ( from ( ( the ( sperm cell ) ) ( that produced ) ) ) ) fertilization ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN Once) (S (NP (DT the) (NN ovum)) (VP (VBZ is) (VP (VBN fertilized))))) (, ,) (NP (EX there)) (VP (VBP are) (NP (NP (CD two) (NNS pronuclei)) (, ,) (NP (NP (CD one)) (VP (VBG originating) (PP (IN from) (NP (NP (DT the) (NN ovum)) (, ,) (NP (DT the) (ADJP (JJ other) (PP (IN from) (NP (NP (DT the) (NN sperm) (NN cell)) (SBAR (WHNP (WDT that)) (S (VP (VBD produced))))))) (NN fertilization)))))))) (. .)))
Once the ovum is fertilized, there are two pronuclei, one originating from the ovum, the other from the sperm cell that produced fertilization.
(ROOT (S (SBAR (IN While) (S (NP (NNS spermatogenesis)) (VP (VBZ produces) (NP (CD four) (JJ haploid) (NN sperm) (NNS cells))))) (, ,) (NP (NNS oogenesis)) (VP (VBZ produces) (NP (CD one) (JJ mature) (NN ovum))) (. .)))