Evidence on major gene control of cortical index in pedigree data from Middle Dalmatia, Croatia

It was recently reported that the inheritance of the metacarpal cortical in dex ICI) in the Chuvashian population can be described in terms of a major gene (MG) model. By applying transmission probability tests, the hypothesis was accepted that not only baseline level of CI but also its sex-specific dependence on age were under control of the same putative large-effect gene . Using a pedigree sample from the population of the islands of Middle Dalm atia, Croatia (847 observed individuals in 278 pedigrees), data are present ed to support the above findings. The following hypotheses were accepted: ( i) inheritance of baseline CI in the Croatian population can be attributed to the effect of a R IG responsible for about 42% of the variation: (ii) th e same MG takes part in the control of the dependence of CI on age, particu larly the age at onset of involutive bone changes (inflection point), and o f the rate of decrease in CI with age (slope coefficient). Issues related t o the assortative mating effect on CI and the determination of the most par simonious model are discussed. (C) 2001 Wiley-Liss, Inc.