( ( ( ( ( ( Mice ( lacking ( ( one copy ) ( of ( the gene ) ) ) ) ) ( ( turned out ) ( to ( mirror ( precisely ( the ( human disease ) ) ) ) ) ) ) , ) and ) ( ( mice ( lacking ( both copies ) ) ) ( have ( ( a skeleton ) ( ( ( ( made entirely ) ( of cartilage ) ) , ) ( like ( little sharks ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (NP (NNS Mice)) (VP (VBG lacking) (NP (NP (CD one) (NN copy)) (PP (IN of) (NP (DT the) (NN gene)))))) (VP (VBD turned) (PRT (RP out)) (S (VP (TO to) (VP (VB mirror) (NP (RB precisely) (DT the) (JJ human) (NN disease))))))) (, ,) (CC and) (S (NP (NP (NNS mice)) (VP (VBG lacking) (NP (DT both) (NNS copies)))) (VP (VBP have) (NP (NP (DT a) (NN skeleton)) (VP (VBN made) (ADVP (RB entirely)) (PP (IN of) (NP (NN cartilage))) (, ,) (PP (IN like) (NP (JJ little) (NNS sharks))))))) (. .)))
Mice lacking one copy of  the gene turned out to mirror precisely the human disease, and mice lacking both copies have a skeleton made entirely of cartilage, like little sharks.
(ROOT (S (ADVP (RB Early) (PP (IN in) (NP (NP (DT the) (NN development)) (PP (IN of) (NP (DT a) (JJ human) (NN fetus)))))) (, ,) (NP (DT the) (NN skeleton)) (VP (VBZ is) (VP (VBN made) (ADVP (RB entirely)) (PP (IN of) (NP (NN cartilage))))) (. .)))