( ( When ( ( ( ( an ovum ) and ) ( a ( sperm cell ) ) ) unite ) ) ( , ( they ( ( ( produce ( a ( complete cell ) ) ) ( with ( 46 chromosomes ) ) ) . ) ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NP (DT an) (NN ovum)) (CC and) (NP (DT a) (NN sperm) (NN cell))) (VP (VB unite)))) (, ,) (NP (PRP they)) (VP (VBP produce) (NP (DT a) (JJ complete) (NN cell)) (PP (IN with) (NP (CD 46) (NNS chromosomes)))) (. .)))
When an ovum and a sperm cell unite, they produce a complete cell with 46 chromosomes.
(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))) (. .)))