ABSTRACT
The Duchenne muscular dystrophy (DMD) gene is the largest human gene identified, spanning more than 2000 kb of genomic DNA, and is composed of 79 exons that encode a 14-kb transcript which is translated into a protein named dystrophin (1,2). It has been observed that approximately 60% to 65% of the mutations that cause DMD/BMD are large deletions in the dystrophin gene (3,4). The distribution of deletions within the DMD gene of DMD/BMD patients studied at The Ohio State University is shown in Figure 1. The deletions are nonrandomly distributed and occur primarily in the center (approximately 80%) and less frequently near the 50 end (approximately 20%) of the gene. The 200-kb region covering intron 44, exon 45, and intron 45 is the major deletion breakpoint region of the gene. The majority of the larger deletions are found to initiate at the 50 end of the gene. The distribution of deletions (Fig. 1) has been demonstrated in many populations and ethnic groups.
