[Preliminary study on RFLPs for dystrophin gene in Chinese]

We have studied the RFLPs distribution and frequency of dystrophin gene in Chinese by using 14 subclones of complete 14 kb cDNA for the dystrophin gene as hybridization probes. Allelic fragments are detected in hybridization patterns of Pvu II/1a, Taq I/2b-3, Taq I/5b-7, Xba I/10. Among them, the allelic fragments (26 kb and 3.8 kb) in Pvu II/2b-3 patterns and the allelic fragments (10 kb and 8.4 kb) in Taq I/5b-7 patterns are the new RFLPs which have never been reported. From the comparison of our data with those of Caucasian and Japanese respectively and their statistical analysis, we can obtain the results as follows: There is remarkable difference (p less than 0.01) of the allelic fragment frequency in Taq I/2 b-3 (A1 = 3.4 kb, fre. 0.04; A2 = 3.2 kb, fre. 0.96) and Xba I/10 (A1 = 7.4 kb, fre. 0.41; A2 = 6.7 kb, fre. 0.59) between Chinese and Caucasian. The frequency of the allelic fragments A2 in Taq I/8 (A1 = 6.5 kb, A2 = 5.6 kb) and EcoR V/9 (A1 = 11.8 kb, A2 = 10.7 kb) are high in Caucasian, but have not been detected in Chinese. These differences are also highly significant. But the B1B2 allelic frequencies in Taq I/5 b-7 (B1 = 3.2 kb, B2 = 1.6 kb) are the same. There is no significant difference in the frequency of the allelic fragments A1A2 and B1B2 in Pvu II/1 a between Chinese and Japanese. Preliminary results suggest that there probably are high frequencies for spontaneous neutral mutations in the evolution process of the huge dystrophin gene (about 2,300 kb). In the meantime, the neutral mutation frequencies of various sectional sequences have remarkable differences, and that of some sectional sequences of the gene between Chinese and Caucasian may also have remarkable differences.