Twinning and Blood Groups — II. Distribution of ABO, MN and Rh-Hr Phenotypes in a Twin Sample

Abstract

The distribution of ABO, MN and Rh-Hr phenotypes has been examined in a sample of 688 twin pairs, with particular emphasis on the ABO distribution. It appears that MZ and DZ pairs exhibit opposing deviations from the expected distribution; such deviations tend to cancel out each other in the total sample, thus masking the phenomenon. The results are briefly discussed, calling for an extension of the study to the twins' families, while forthcoming papers will present further analyses.