( This ( ( ( ( ( may ( happen ( when ( ( a ( diploid ( cell undergoes ) ) ) ( ( ( failed meiosis ) , ) ( producing ( diploid gametes ) ) ) ) ) ) ) , ) and ) ( self-fertilizes ( to ( produce ( a ( tetraploid zygote ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This)) (VP (VP (MD may) (VP (VB happen) (SBAR (WHADVP (WRB when)) (S (NP (DT a) (JJ diploid) (NN cell) (NNS undergoes)) (VP (VBD failed) (NP (NNS meiosis)) (, ,) (S (VP (VBG producing) (NP (JJ diploid) (NNS gametes))))))))) (, ,) (CC and) (VP (VBZ self-fertilizes) (S (VP (TO to) (VP (VB produce) (NP (DT a) (JJ tetraploid) (NN zygote))))))) (. .)))
This may happen when a diploid cell undergoes failed meiosis, producing diploid gametes, and self-fertilizes to produce a tetraploid zygote.
(ROOT (S (NP (NP (JJ Sexual) (NN reproduction)) (PP (IN with) (NP (NNS gametes) (CC and) (NN fertilization)))) (VP (VBZ produces) (NP (JJ diploid) (NN sporophyte))) (. .)))