The overwhelming majority of CMT1A duplications (nine in nine cases as reported in [46] and 26 in 28 cases in [47]) as well as 85% of spinal muscular atrophy (SMA; MIM253300) deletions [48] originate in spermatogenesis; whereas 80% of NF1 deletions are of maternal origin [8,49]. This evidence concerns the gene NF1 and proximal spinal muscular atrophy.