The importance of zygosity knowledge for twins, parents and professionals

Zygosity refers to the degree of genetic similarity within each pair of twins. Monozygotic (identical) twins have the same genetic sequence, whereas dizygotic twins differ genetically as much as any pair of siblings. Accurate knowledge of zygosity is important for a range of reasons; yet incorrect information on whether twins are monozygotic or dizygotic is still given to twins and their parents. This article focuses on why zygosity testing is so important medically, socially, financially and ethically/.