Which statement about monozygotic twins is correct?

The statement that monozygotic twins share 100% of their genetic material is correct. Monozygotic twins, also known as identical twins, originate from a single fertilized egg that divides into two embryos. Because they come from the same fertilized egg, they have identical genetic information, making them genetically the same. This genetic identity results in physical and sometimes behavioral similarities between the twins.

The other statements present inaccuracies about the nature of monozygotic twins. For instance, monozygotic twins are not formed from separate fertilized eggs—this is a characteristic of dizygotic twins. Additionally, while monozygotic twins typically have the same gender due to their identical genetic material, there are rare exceptions where differences can occur, primarily due to chromosomal abnormalities during development. Lastly, the process that creates monozygotic twins occurs when a single fertilized egg, after several divisions, splits into two, not when the morula does not split. Therefore, the correct response accurately reflects the unique genetic relationship that defines monozygotic twins.