Identification and quantification of somatic mosaicism for a point mutation in a Duchenne muscular dystrophy family

Relatively few point mutations have been found in the dystrophin gene and o f these only two have been associated with mosaicism. A single base inserti on has been identified and quantified in a mother of two sons affected with Duchenne muscular dystrophy. It has been determined that she is a somatic mosaic with the mutation present in 25% of lymphocyte DNA. Further tissue l ineages have been tested and the time at which the mutation arose was deter mined to be before the cellular differentiation into the bilaminar disc at approximately eight days after fertilisation. We suggest that the incidence of mosaicism for dystrophin point mutations may be higher than current dat a suggest.