title: Coefficients of relationship by isonymy among the parents of Scottish twins: a test of familial aggregation.
abstract: The ability of the coefficient of relationship by isonymy Ri to detect familial aggregation of conditions suspected of being under a degree of genetic control was tested on groups of fathers and mothers of like-sex twins, fathers and mothers of unlike-sex twins, and fathers and mothers of singleton controls born from 1977 to 1981 in Scotland. No statistically significant difference of within-group or between-group Ri was found, either for all surnames or for rare surnames only. However, the overall pattern of results for rare surnames showed a measure of agreement with what is already known of the genetics of twinning. The relatively high within-group Ri for mothers of unlike-sex twins is consistent with a maternal genetic influence on dizygous twinning, whereas the relatively high between-group Ri for fathers with mothers of unlike-sex twins suggests that paternal as well as maternal genes may be involved. Values of Ri for the parents of like-sex twins raise the possibility of a paternal but not a maternal genetic contribution to monozygous twinning.
authors.affiliation: Human Genetics Unit, University of Edinburgh, United Kingdom.
authors.forename: S M
authors.initials: SM
authors.lastname: Holloway
authors.forename: J A
authors.initials: JA
authors.lastname: Sofaer
mesh_terms: D005190:Family; D005260:Female; D005828:Genetics, Population; D006801:Humans; D008297:Male; D012606:Scotland; D009626:Terminology as Topic; D014427:Twins / Q000235:genetics*