Heredity of Twinning in Families of Monozygotic Twins

Abstract

Whereas the existence of some genetic factor underlying the phenomenon of twinning is almost generally accepted with respect to DZ twins, no such agreement exists with respect to MZ twins. The possible existence of genetic factors underlying MZ twinning has been verified through an analysis of segregation in the sibships of MZ twins and in those of their parents, carried out on a sample of 57 MZ twin pairs (30 M and 27 F). Haldane's a priori method has been applied, considering the sample as obtained through a complete and through an incomplete ascertainment. The results may lead to cautiously confirm the hypothesis of some genetic conditioning of MZ twinning.