Intrapair Comparisons of Total Life Span in Twins and Pairs of Sibs

The Mormon Genealogy Data Base has been used to compare longevity of twins with that of pairs of sibs in the same sibships. The data consisted of twins and sibs born between 1810 and 1899 whose Family Record Sheets were on file. We excluded all pairs in which at least one of the sibs or twins died in infancy.The findings show that twins are disadvantaged in comparison with their other sibs. Sib-sib life span associations were significant but lower than the corresponding correlations in all twin pairs, including the opposite-sex pairs. No significant associations were found between a twin and the next older sib. The special environmental constitutes of twins compared with sibs born to the same parents are corroborated by these findings. It is suggested that maternal mortality accounted for shorter life span in female compared with male twins. This relation was not evident when comparing the survivorship curves of female and male sibs

The Genetic Origin of the Jews: A Multivariate Approach

An analysis of 12 Jewish populations and 20 non-Jewish populations living in four geographic areas was carried out by first discriminating between the non-Jewish populations of Central Europe, South Europe, North Africa, and the Middle East using four genetic markers (ABO, MN, Rh, Hp). This discrimination was quite successful when applied to the non-Jewish groups in predicting the geographic origin of a population. These discriminant functions were then used to classify the Jewish groups. A wide scatter of the Jews was observed among clusters of non-Jews, probably due to drift. However, the centroid of the Jewish populations mapped in the Middle East cluster. Direct estimates of admixture with local populations and of effective Jewish population size Ne were made. The latter are in qualitative agreement with expectations from historical and geographical considerations

Segregation Analysis Reveals a Major Gene Effect Controlling Systolic Blood Pressure and BMI in an Israeli Population

It has been suggested that genetic factors control blood pressure level at all ages. However, the evidence is limited because of the composite nature of blood pressure and the heterogeneity of the studied samples. The purpose of the present study is to test for genetic influences on systolic blood pressure (SBP) level in a community-based Israeli family study. Segregation analysis was performed on 622 adults from 208 pedigrees. Age, sex, and body mass index (BMI) were significant covariates of SBP. Segregation analysis rejected the environmental transmission model but not the mixed Mendelian transmission model. The bestfitting genetic model was the mixed codominant model, with a heritability of 0.32 and an allele frequency of 0.18 for high SBP level. We further tested whether SBP and BMI shared a common major gene effect. Using bivariate segregation analysis involving two traits and a single locus, we found evidence for a single-locus pleiotropic effect on SBP and BMI. The allele frequency of this major locus was 0.24. The residual genetic correlation resulting from additive polygenes and the environmental correlation between these two traits were not different from zero after taking into account the shared major gene effect. The proportion of phenotypic variation attributable to this major gene effect increased with age for SBP but decreased with age for BMI