A new PstI restriction fragment length polymorphism (RFLP) of placental alkaline phosphatase. RFLP haplotypes and correlation with electrophoretic types.

A new PstI restriction fragment length polymorphism (RFLP) of placental alkaline phosphatase (PLAP) was discovered in a study of a Finnish population sample and designated PstI(b)1 or Pst(b)2 depending on the presence or absence of the cleavage site. The frequency of the PstI(b)2 allele was 0.24. This allele showed a positive (p = 3 x 10(-6) association with the electrophoretic allele 2(F) and a negative association (2 x 10(-7) with the electrophoretic allele 1(S). The previously described PstI RFLP [PstI(a)] was also found to be associated with electrophoretic types; the PstI(a)1 allele (presence of site) was associated with the electrophoretic type 2 (p = 0.023). Haplotype frequencies and disequilibria were calculated between PstI(a), PstI(b) and RsaI RFLPs. A complete disequilibrium (p = 1 x 10(-6) was found between PstI(a) and RsaI, whereas there was no significant disequilibrium between PstI(b) and RsaI. There was no strict correlation between the distances between the RFLP loci and the degree of linkage disequilibrium. The allele controlling the electrophoretic variant PLAP 18 (D) was found in polymorphic frequency (0.024) in the Finnish population.