Interesting example of CRISPR mouse knockout strategies

Many traditional mouse knockouts have generated results that were not straightforward to interpret, or even controversial.   CRISPR promises to allow more replication experiments, or varying targeted designs, to sort out some of these issues as discussed in the Prp/Prnp story:

http://www.cureffi.org/2014/03/09/how-to-and-how-not-to-knock-out-prnp/