Solenoid (genetics)

The Solenoid is a packaging structure in DNA that results from the helical winding of at least five nucleosome strands. DNA packed into solenoids, unlike DNA in nucleosome form, is not transcriptionally active. With more packing, solenoids are able to become increasingly more packed, forming chromosomes. At this point, solenoids coil around each other to form a loop (anywhere from 20 to 80,000 base pairs), followed by a rosette (consisting of six connected loops), then a coil, and at last, two chromatids. The end result is the metaphase chromosome. The completely condensed chromatin has a diameter of up to 600 nm.