Chromosome structure.
<P>
   Interactions  between nucleosomes cause the 10-nm fiber to coil into a
   30-nm fiber.
<P>
   The  30-nm  fiber  forms  looped  domains that attach to a scaffold of
   non-histone proteins.
<P>
   The  looped  domains  coil  further  during  mitosis  to form a 700-nm
   chromatid.
<P>
   Such tight packing makes the genes on the DNA inactive.