CHRNA7 and Prader-Willi syndrome: Other rearrangements appear to be much more common, such as the BP2/BP3 inversion and the probable persistence of a pre-CHRFAM7A structure that predates the partial duplication of CHRNA7. Their phenotypes appear to be normal, although the former confers an increased risk for PWS/AS in the next generation, and there is some evidence that the latter may predispose to the major psychoses.