Final answer:
The looping of DNA around histone proteins occurs because of the winding of DNA strands around histone proteins to form nucleosome complexes.
Step-by-step explanation:
The looping of DNA around histone proteins occurs because of the winding of DNA strands around histone proteins to form nucleosome complexes. Histones package and order DNA into structural units called nucleosomes, which can control the access of proteins to the DNA regions. Under the electron microscope, this winding of DNA around histone proteins looks like small beads on a string.