( Unfortunately ( , ( one ( ( ( can not ) ( generate ( embryos ( ( lacking ( ( the function ) ( of ( either gene ) ) ) ) ( because ( ( both genes ) ( have ( ( a ( strong ( maternal contribution ) ) ) ( that ( is ( required ( for oogenesis ) ) ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (ADVP (RB Unfortunately)) (, ,) (NP (PRP one)) (VP (MD can) (RB not) (VP (VB generate) (NP (NP (NNS embryos)) (VP (VBG lacking) (NP (NP (DT the) (NN function)) (PP (IN of) (NP (DT either) (NN gene)))) (SBAR (IN because) (S (NP (DT both) (NNS genes)) (VP (VBP have) (NP (NP (DT a) (JJ strong) (JJ maternal) (NN contribution)) (SBAR (WHNP (WDT that)) (S (VP (VBZ is) (VP (VBN required) (PP (IN for) (NP (NNS oogenesis))))))))))))))) (. .)))
Unfortunately, one cannot generate embryos lacking the function of either gene because both genes have a strong maternal contribution that is required for oogenesis.
(ROOT (S (NP (CD One) (JJ large) (NNS eggs)) (VP (VBP are) (VP (VBN generated) (PP (IN during) (NP (NNS oogenesis))))) (. .)))