A genetic model for the inheritance of the P, P1 and Pk antigens.

A new genetic model of the P blood group system is presented. The system is controlled by two chromosomal loci. The first locus has three allelic genes. The pk gene codes for an alpha galactosyl transferase that converts ceramide dihexoside to ceramide trihexoside (or the pk antigen). The second allele, the pk gene, codes for an alpha galactosyl transferase that converts both ceramide dihexoside to ceramide trihexoside (or the pk antigen) and paragloboside to the P1 antigen. The third allele does not produce an active codes for a beta N-acetyl galactosaminyl transferase that converts ceramide trihexoside to globoside (or the P antigen). The second allele does not produce an active product. The predictions of the model are in agreement with family studies and fibroblast fusion studies. The current model and previous genetic models, however, predict different possible phenotypes from rare 2 x p or p2k x p matings or fibroblast fusions.