What is the key characteristic of monozygotic twins?

Monozygotic twins, commonly referred to as identical twins, are formed from a single fertilized egg that splits into two embryos. This unique process results in two individuals who share nearly the same genetic material, leading to their physical resemblance and often similar traits. The key characteristic of monozygotic twins is their genetic identity, which contrasts with dizygotic twins, who originate from two separate eggs and sperm and thus have different genetic makeups.

While other characteristics such as shared structures or the presence of a single placenta can be observed in certain cases, the defining aspect that sets monozygotic twins apart is their identical genetic composition, making this the most accurate representation of their nature.