User blog comment:Omega natsu2/Chapter 373: Let Live Or Let Die, Predictions./@comment-24551285-20140224070236/@comment-7418318-20140225191342

Just to clarify one of my points, since it didn't seem all that clear to me when I re-read my previous comment:

I didn't mean to say that Karin can sense DNA, but it's possible that due to all the fiddling he did with his body, Kabuto's chakra signature (or whatever you want to call it) might have changed enough for Karin to no longer recognize it.