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Nineteen out of the 53 blood donors of french village with 241 inhabitants (Cezay Loire) are Rh negative (D--). This discrepancy in the distribution is analysed. 1.--The study of the genetic erythrocyte markers (ABO and Rh system for 158 inhabitants, Kell, Rautenberg, Duffy, Kidd, MNSs, P1 Lutheran, PGM1, PGM2, 6 PGD, AK, ADA, Acid phosphatase systems for 104 inhabitants) show significant abnormal gene frequencies (No. 10%) compared with a control population from Saint-Etienne, for A1, Ms, r, P1 alleles; conversely rare alleles do not seem to exist. HLA system was not tested. 2.--The genetic study led to: a) a demographic study which implied 7840 registrar's certificates and the building up of 1364 families to which the 5096 subjects belonged identified and having lived in Cezay since 1607 (this date corresponds to the earliest registrar's certificate). b) it also led to the analysis of the origin and evolution of the genetic inheritance throughout the 13 generations of known inhabitants. The calculation of the chances of each generation having passed on its genetic material to following generations shows that: Cezay has an integrated population; 30% of the genes are renewed for each generation the average value of each founder can vary according to the various generations but there seems to exist a "founder effect" of the Rh--(D--) having been and lived in the village before 1860. Although they represent 68% of the total population, the tested samples can be contested for certain systems, in its constitution (formation, choice) which prevents from ascertaining the foundation effect observed. The authors underligne the contribution of immunogenetics to the genetics of populations, and show the incidence of the choice of samples in the method used.

The adenosine deaminase gene frequencies were calculated in 405 subjects randomly chosen from the Bigouden district. A rather high frequency (0.0765 +/- 0.0093) was found for the ADA2 gene. The possible effect of Celtic influences is considered.

Data are presented on the red cell enzymes of the Bigoudens. Deviations fro the expected Hardy-Weinberg distribution are interpreted as the result of a recent mixing of previously separated groups, in addition to the effect of silent alleles and inbreeding. Special reference to the historical background.

A total of 386 and 393 members of a Breton community, in France, the Bigoudens, have been tested for polymorphisms of C3 and haptoglobin (Hp) plus Transferrin (Tf) respectively. An interesting observation was a gap between the observed and expected phenotype C3 frequencies. The Hp and Tf gene frequencies were not found to be closer to the other Celtic peoples than to the French and English populations.