Final answer:
The compaction of eukaryotic chromosomes into radial loop domains is controlled by the nuclear envelope.
Step-by-step explanation:
In eukaryotic cells, the compaction of chromosomes into radial loop domains is the function of the nuclear envelope.
The nuclear envelope consists of a double membrane that surrounds the nucleus, separating it from the rest of the cell.
It plays a critical role in organizing and condensing the DNA through interactions with proteins such as histones and scaffold proteins.