FREQUENCY OF THE G6PD NT-1311-C T POLYMORPHISM IN ENGLISH AND IRANIANPOPULATIONS - RELEVANCE TO STUDIES OF X-CHROMOSOME INACTIVATION/

X chromosome inactivation is widely studied using DNA sequence polymor phisms and DNA methylation as a surrogate measure of inactivation, but the correlation of methylation with inactivation is not perfect. Thus , it may be better to study sequence polymorphisms expressed in the mR NA. A recent paper reported use of a silent C/T polymorphism at nt 131 1 of the G6PD cDNA, and this polymorphism was reported to have a frequ ency of 40% in all ethnic groups. We have screened 218 English and 50 Iranian subjects by PCR and restriction digestion; 53/218 (24%) Britis h and 22/50 (44%) Iranian subjects were heterozygous. Thus, X inactiva tion studies using this polymorphism may be useful in some populations , including Iran, but much less so in the UK.