Linkage analysis of polymorphisms within the DNA fragment XJ cloned from the breakpoint of an X;21 translocation associated with X linked muscular dystrophy.

Abstract

SUMMARY Cloning of a DNA segment including the translocation breakpoint in a female with an X;21 translocation and X linked muscular dystrophy has led to identification of three subclones which detect polymorphic markers. The alleles of these markers, XJ1 1, XJ1-2, and XJ2 2, are in strong linkage disequilibrium. Linkage analysis in 31 families with Duchenne or Becker muscular dystrophy has shown recombination within the XJ segment in one case, and recombination of DMD with both the XJ segment and the pERT87 segment in a second, but has revealed no recombination between the XJ and pERT87 segments. The XJ markers increase the proportion of DMD and BMD families that are informative for carrier detection and prenatal diagnosis, but in view of the risk of recombination they must be used with caution. The site(s) of the DMD mutation(s) relative to the XJ and pERT87 markers, and the detailed molecular structure of the DMD region, remain to be determined.The locus for Duchenne muscular dystrophy (DMD)

Restriction fragment length polymorphisms on the short arm of X chromosome among the Japanese population

“…For example, the restriction fragment length has been reported as 12.0 or 9.0 kb for the probe 754 after digestion with a Kunkel et al (1986) for probes pERT87-15, 87-8 and 87-1, Thompson et al (1986) for probe XJI.1, Worton (1987, personal communication) for probe XJ5.1, and Willard et al (1985) for other probes.…”

The problem of Duchenne muscular dystrophy

“…The third indication of a large gene came from family studies in which rflp markers from the P E R T 87 (Fischbeck et al 1986;) and X J (Thompson et al 1986) region were found to segregate with the dmd gene in only 9 5 % of meioses. In 5 %, a recombination event took place in the chromosome interval between the site of m utation and the site of the probe.…”