[Difference of new mutation rates in dystrophin gene between deletion and duplication mutation in Duchenne and Becker muscular dystrophy].

To clarify new mutational rates in the dystrophin gene between deletion and duplication mutations, carrier diagnosis was performed on 123 mothers of probands suffered from Duchenne (DMD) and Becker (BMD) muscular dystrophy. Quantitative Southern blot analysis with cDNA probes was applied in this study. Out of 108 mothers of DMD/BMD patients with deletion mutation in dystrophin gene, 69 were carriers and 39 were non-carriers. On the other hands, all of 15 mothers of probands with duplication mutation were carriers. The fact that no new mutation occurred in oogenesis in the families with duplication mutations in dystrophin gene indicates that duplications arise in spermatogenesis. The risk of the mother of an isolated case of DMD/BMD with duplication mutation of being a carrier is significantly higher than the estimated risk based on the equality of new mutation in oogenesis and spermatogenesis.