Zygosity Determination Done by the Twin Registry

The Washington State Twin Regsitry uses a form of zygosity determination called “self-report.” This determination uses the responses that you and your twin provided to two questions on the registry recruitment survey: “When you and your twin were children, were you as alike as two peas in a pod or of ordinary family resemblance?”; and “How often did parents, relatives, teachers, and strangers have trouble telling you and your twin apart?”

Based on the answers that you and your twin provide and comparing your answers with those of other twins in the Registry, we have developed a method that can predict zygosity with about 96% accuracy. We use this “self-report” zygosity to generate the statistics for our website and to recruit twins for our studies. This method is statistically useful as it accurately reflects group trends and tendencies. To read about how we developed this method, click here.