ABO and Rh blood groups in the Outer Hebrides.

ABO and Rh (D--,dd) phenotype frequencies and gene frequencies are reported on 1547 pregnant women from different populations in the Outer Hebrides. There was significant heterogeneity of ABO gene frequencies in the Isle of Lewis, but not in or between other populations. More heterogeneity was apparent at the Rh locus, significant amounts being present between the populations of rural Lewis, between Lewis and Harris and between Lewis, Harris and the combined populations of North and South Uist, Benbecula and Barra. There was no evidence of heterogeneity due to religion in Benbecula or South Uist. Data on exogamy and endogamy suggest that migration between the various populations has been at a level sufficient to prevent or correct any tendency to genetic diversification. It is suggested tentatively that the heterogeneity observed may be the result of the massive emigration from the islands which has occurred over the last 150 years.