LINKAGE DISEQUILIBRIA AMONG (CA)(N) POLYMORPHISMS IN THE HUMAN DYSTROPHIN GENE AND THEIR IMPLICATIONS IN CARRIER DETECTION AND PRENATAL-DIAGNOSIS IN DUCHENNE AND BECKER MUSCULAR-DYSTROPHIES

Four short tandem repeat loci, characterized by length polymorphisms o f (CA)(n) repeats, have been detected within introns 44, 45, 49, and 5 0 of the human dystrophin gene. The predicted heterozygosities for the se loci range from 72 to 93%, and observed allele numbers range from 6 to 19 in 57 normal chromosomes, revealing their high degree of polymo rphism. Evidence for significant disequilibria between the loci within introns 49 and 50 is found. These data appear to be consistent with o bservations of recombination frequencies between these markers and the length of the intron 44 in relation to the entire region. In addition , these four loci are collectively found to be 100% informative in car rier detection/prenatal diagnosis of Becker and Duchenne muscular dyst rophies (B/DMD), whereas scoring the (CA)(n) markers within introns 45 and 49 alone gives a 99.6% success rate. (C) 1994 Academic Press, Inc .