Twin studies Concordance both twins display phenotype in question Discordance= one twin displays phenotype in question, other does not Concordance Rates in MZ twins Dz twins Interpretation Huntington's disease 100% 50% autosomal dominant Sickle cell disease 100% 25% autosomal recessive Cystic fibrosis 100 25% autosomal recessive Measles 97% 94% environmental (contagious) Cleft lip 40% 4% environment multiple genes Insulin-dependent 30% 6% environment,≥1gene diabetes Coronary heart disease 46% 12% environment,≥1gene Schizophrenia 46% 14% environment,≥1geneMZ twins DZ twins Interpretation Concordance Rates in environmental (contagious) environment + multiple genes Twin studies: Concordance = both twins display phenotype in question Discordance = one twin displays phenotype in question, other does not Schizophrenia Coronary heart disease Insulin-dependent diabetes Cleft lip Measles Cystic fibrosis Sickle cell disease Huntington's disease 100% 50% autosomal dominant 100% 25% autosomal recessive 100% 25% autosomal recessive 97% 94% 40% 4% 30% 6% environment, ≥1 gene 46% 12% environment, ≥1 gene 46% 14% environment, ≥1 gene