Analysis of the GGAA minisatellite repeat of the erythropoietin receptor gene in three polycythemic Chuvash patients and some of their first-degree relatives. As shown in the autoradiogram of the PCR analysis of this locus, several different alleles are present in the affected subjects, in their parents (obligate carriers assuming autosomal recessive inheritance), and in siblings. Because the subjects with polycythemia are not homozygous for one or a restricted number of alleles, these data do not suggest linkage of polycythemia to the erythropoietin receptor gene.