Yamato has the first's sealing ability. Sakura asked if he would teach her the technique, but Yamato said he can't because the only reason he could use it was because he had the first DNA. Well the question I have is: Why can't they implant the first's genes into her? Yes, I know Yamato ends up getting killed later. The leaf has much better medical abilities than Orochimaru had on his own so wouldn't it be possible without killing Sakura?