DNA polymorphism of the RC8 sequence on the short arm of the X chromosome in a French population.

Restriction fragment length polymorphism of the RC8 probe, which is loosely linked to the Duchenne muscular dystrophy locus, was studied in a French population. Among 22 females, 18.1% were found to be heterozygous for the two frequent B1 and B2 alleles, and a rare allele was found in 1 woman with a corresponding variant band at 3 kb. Among 18 males, 6 were found to have the B2 allele. The B2 gene frequencies were 0.09 and 0.33 in males and females, respectively. This difference was statistically significant (p less than 0.05), but may nevertheless be fortuitous. There was no significant gene frequency difference between the English and French populations.