How do monozygotic twins differ from dizygotic twins?

Monozygotic twins, also known as identical twins, originate from a single fertilized egg that splits into two embryos. This process results in two individuals who share nearly 100% of their genetic material, leading to the conclusion that they have similar genomes. Because they come from the same fertilized egg, they typically exhibit very similar physical traits and genetic characteristics. This genetic similarity is the primary distinguishing feature between monozygotic twins and dizygotic twins, who develop from two separate eggs fertilized by two separate sperm cells and share about 50% of their genetic material, similar to regular siblings.

Understanding the genetic relationship in twin studies is important in psychology and social science, particularly in research related to heredity and environment. The significant genetic similarity in monozygotic twins allows researchers to explore the influences of genetics versus environment in various traits and conditions.