Final answer:
The next level of folding after the 30-nm fiber formation involves a structure supported by fibrous proteins, which leads to further compaction and organization of the chromatin within the nucleus.
Step-by-step explanation:
After the arrangement of nucleosomes into a 30-nm fiber, the next level of folding involves the formation of a structure facilitated by a variety of fibrous proteins. These fibrous proteins enable further compaction of the chromatin, ensuring that each chromosome occupies a specific area within the nucleus that does not overlap with any other chromosome. This results in densely packed chromatin, reducing its size significantly compared to the stretched out form of DNA. Ultimately, this level of compaction is critical for the efficient segregation of chromosomes during cell division.