Prevalence and inheritance of C3 types in the Polish population.

In a sample of the Polish population numbering 1,458 subjects, the three common types, C3S, C3F and C3FS, were found with frequencies of 0.6790, 0.0295 and 0.2901 respectively, besides two rare variants, C3FO, 7S and C3SO, 25S. Frequencies of C3S and C3F genes were 0.8248 and 0.1746 respectively, and of the CSFO,7 and C3SO,25 genes, 0.0003 each. Distribution of types in 695 mother-child pairs was consistent with the hypothesis that the C3 system depends on a single genetic locus in which codominat alleles are situated. No children of C3S and C3F mothers with opposite homozygous types were encountered. Hereditary character of the C3FO, 7S variant was confirmed by family studies in which the rare C3FO,7 gene, in combination with C3S or C3F genes, occured in three generations.