Final answer:
The statement is partially true.
Step-by-step explanation:
Nucleosomes themselves are not 30nm in diameter; they form a structure that is 10nm in diameter when DNA is wrapped around histone proteins in what is known as a "beads-on-a-string" fashion. However, when these nucleosomes fold over and compact onto each other with the assistance of a fifth histone (H1), they form the 30nm fiber. This fiber is a secondary structure that provides additional compaction to DNA within the cell nucleus.
The process of DNA packing is crucial for fitting the long DNA molecules into the cell nucleus. The initial wrapping of DNA around histone octamers to form nucleosomes compacts the DNA by approximately seven-fold.
Further coiling of the nucleosomes and associated linker DNA into the 30nm fiber structure provides about 50 times shorter length than the extended form. Finally, during mitosis, chromatin fibers condense even further, with metaphase chromosomes reaching a width of approximately 700 nm, associated with scaffold proteins.