Gene localisation of the PGM1 enzyme system and the Duffy blood groups on chromosome No. 1 by means of a new fragile site at 1p31.

During routine paternity testing an apparent maternal exclusion was suggested by the PGM1 enzyme system (mother PGM1 1, child PGM1 2) and by the Duffy system (mother Fy(a-b+), child Fy(a+b-]. To clarify these findings chromosomal analyses and anthropological investigations were carried out. The possibility that the child had been mistakenly identified after birth could be eliminated. Chromosome analysis of the child showed a fragile site on one chromosome No. 1 at 1p31, a position supposed to carry the PGM1 and the Duffy loci. Although the father of the child is unknown, paternal origin of the fragile site is unlikely on account of the coincidence of the structural aberration with the missing expression of the maternal PGM1 and Duffy alleles thought to be located at the chromosome region involved. Thus localisation of the PGM1 and Duffy loci on 1p31 seems to have been achieved in an unusual way. The two loci appear to be closely linked.