AP BIOLOGY

Detailed explanation-1: -We can define three levels of chromatin organization in general terms: DNA wrapped around histone proteins (nucleosomes) like “beads on a string”. Multiple nucleosomes coiled (condensed) into 30 nm fiber (solenoid) structures. Higher-order packing of the 30 nm fiber into the eventual familiar metaphase chromosome.

Detailed explanation-2: -The first level of packing is thought to produce a fiber about 30 nanometers (nm) wide. These 30 nm fibers then form a series of loops, which fold back on themselves for additional compacting (Figure 5).

Detailed explanation-3: -Abstract. Three levels of structural organization of eukaryotic DNA in the cell nucleus are considered in this paper: (i) the chain of nucleosomes; (ii) the solenoidal or superbead (nucleomere) model of compactization of the nucleosomal fiber; (iii) the mode of suprasolenoidal DNP-packing–loops or domains.

Detailed explanation-4: -The human genetic material is packed hierarchically within the metaphase chromosome: the DNA molecule together with histone proteins form 11 nm diameter nucleosomes, which are then ordered into the 30 nm thick chromatin fiber.