Objective To study the human dystrophin gene molecular deletion mechanism, we analyzed breakpoint regions within junction fragments of deletion-type patients and investigated whether the dystrophin gene’s intron structure might be related to intron instability.Methods Junction fragments corresponding to exon 46 and 51 deletions were cloned. The breakpoint regions were sequenced, and the features of introns with available Genebank sequences were analyzed.Results An analysis of junction fragment sequences corresponding to exon 46 and 51 deletions showed that all 5’ and 3’ breakpoints are located within repeat sequences. No small insertions, small deletions, or point mutations are located near the breakpoint junctions. By analyzing the secondary structure of the junction fragments, we demonstrated that all junction fragment breakpoints are located in non-matching regions of single-stranded hairpin loops. A high concentration of repetitive elements is found to be a key feature of many dystrophin introns. In Objective To study the human dystrophin gene molecular deletion mechanism, we analyzed breakpoint regions within junction fragments of deletion-type patients and investig whether the dystrophin gene’s intron structure might be related to intron instability. Methods Junction fragments corresponding to exon 46 and 51 deletions were cloned . The breakpoint regions were sequenced, and the features of introns with available genebank sequences were analyzed. Results An analysis of junction fragment sequences corresponding to exon 46 and 51 deletions showed that all 5 ’and 3’ breakpoints are located within repeat sequences. No small insertions, small deletions, or point mutations are located near the breakpoint junctions. By analyzing the secondary structure of the junction fragments, we demonstrated that all junction fragment breakpoints are located in non-matching regions of single-stranded hairpin loops. A high concentration of repetitive elements is found to be a key feature of many dyst rophin introns. In