Final answer:
The infolding theory is supported by the structure of the nuclear envelope which is a double membrane linked to the endoplasmic reticulum and contains nuclear pores allowing selective molecule exchange.
Step-by-step explanation:
The infolding theory that explains the origin of the nuclear envelope suggests that infoldings in the plasma membrane of an ancestral prokaryote led to the development of endomembrane components, including the nucleus and the endoplasmic reticulum. The nuclear envelope itself is a double membrane structure that encloses the genetic material of the cell, separating the contents of the nucleus from the cytoplasm. This envelope's outer membrane is continuous with the rough endoplasmic reticulum, underlining the connection between the two structures and supporting the infolding theory.
Furthermore, the presence of nuclear pores in the nuclear envelope, which facilitate the selective exchange of large molecules such as RNA and proteins, can also be seen as evidence backing this theory. This is because such complex mechanisms for transport could have evolved from simpler membrane structures becoming more specialized and compartmentalized, as suggested by the unfolding process.