( ( ( ( Cleavage and ) Implantation ) ( When ( ( a sperm ) ( penetrates ( the egg ) ) ) ) ) ( , ( it ( ( triggers ( the ( egg ( to ( complete meiosis ) ) ) ) ) . ) ) ) )
(ROOT (S (S (NP (NNP Cleavage) (CC and) (NNP Implantation)) (SBAR (WHADVP (WRB When)) (S (NP (DT a) (NN sperm)) (VP (VBZ penetrates) (NP (DT the) (NN egg)))))) (, ,) (NP (PRP it)) (VP (VBZ triggers) (NP (DT the) (NN egg) (S (VP (TO to) (VP (VB complete) (NP (NNS meiosis))))))) (. .)))
Cleavage and Implantation   When a sperm penetrates the egg, it triggers the egg to complete meiosis.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (DT a) (NN sperm)) (VP (VBZ penetrates) (NP (DT the) (NN egg))))) (, ,) (NP (PRP it)) (VP (VBZ triggers) (NP (DT the) (NN egg) (S (VP (TO to) (VP (VB complete) (NP (NNS meiosis))))))) (. .)))