Germinal mosaicism in Duchenne muscular dystrophy.

We have identified a Duchenne muscular dystrophy (DMD) pedigree where the disease is associated with a molecular deletion within the DMD locus. We have examined the meiotic segregation products of the common female ancestor using marker restriction fragment length polymorphisms (RFLPs) detected by probes that lie within this deletion. These studies show that this female has transmitted three distinct types of X chromosome to her offspring. This observation may be explained by postulating that the mutation arose as a postzygotic deletion within this common ancestor, who was consequently germinally mosaic.