Clinical use of DNA markers linked to the gene for Duchenne muscular dystrophy.
Seventy families with Duchenne muscular dystrophy ( DMD ) known to the Institute of Child Health fall into three categories with respect to potential linkage analysis with the X chromosome DNA markers RC8 and L1 . 28 that bridge the DMD gene . Families in which there is at least one obligatory female heterozygote ( n = 13 ) . Here prediction and exclusion of DMD gene transmission may be possible , the accuracy being dependent on the closeness of the linkage of the DNA marker ( s ) to the DMD gene ; an illustrative case is reported . Families in which there is a single affected boy , who also has one or more healthy brothers ( n = 26 ) . Given an informative restriction fragment length polymorphism ( RFLP ) , the probability that the boy represents a new mutation can be reassessed ; it is also possible to exclude the DMD gene in a sister . Families with a single affected boy with no brother ( n = 30 ) . Here exclusion of the DMD gene in a sister may be possible . Only in one family was there no possibility of useful linkage analysis . The linkage analysis required is described , and the need to check DMD families for informative RFLPs is stressed .
