St14 (DXS52) VNTR in the Chinese population and its application to genetic diagnosis of haemophilia A.

The variable number of tandem repeats (VNTR) of St14 (DXS52) on the human X-chromosome was analysed using the polymerase chain reaction (PCR) method. Screening of 78 X-chromosomes in 56 healthy Chinese individuals revealed the existence of at least seven different alleles in the the Chinese population, the corresponding amplified fragments and frequencies being 700 bp (60.3%), 1220 bp (1.3%), 1300 bp (2.6%), 1390 bp (11.5%), 1570 bp (12.8%), 1630 bp (6.4%) and 1690 bp (5.1%). Total theoretical heterozygous rate was 60%. Compared to Caucasians, this Chinese population showed a markedly higher occurrence of low molecular weight fragments and a relatively low occurrence of high molecular weight fragments. Study of this polymorphism in 14 suspected haemophilia A carriers revealed half of them to be heterozygous. Thus, St14 VNTR analysis by PCR should prove to be a useful tool in the genetic diagnosis of haemophilia A in China.