▁and ▁is ▁local ized ▁within ▁the ▁nucle oid ▁region ). ▁ ▁The ▁overall ▁structure ▁of ▁the ▁chrom atin ▁network ▁further ▁depends ▁on ▁the ▁stage ▁of ▁the ▁cell ▁cycle . ▁During ▁inter phase , ▁the ▁chrom atin ▁is ▁struct ur ally ▁loose ▁to ▁allow ▁access ▁to ▁R NA ▁and ▁DNA ▁polym er ases ▁that ▁trans cribe ▁and ▁rep licate ▁the ▁DNA . ▁The ▁local ▁structure ▁of ▁chrom atin ▁during ▁inter phase ▁depends ▁on ▁the ▁specific ▁gen es ▁present ▁in ▁the ▁DNA . ▁Reg ions ▁of ▁DNA ▁containing ▁gen es ▁which ▁are ▁act ively ▁trans cribed ▁(" turn ed ▁on ") ▁are ▁less ▁tight ly ▁compact ed ▁and ▁closely ▁associated ▁with ▁R NA ▁polym er ases ▁in ▁a ▁structure ▁known ▁as ▁e uch rom atin , ▁while ▁regions ▁containing ▁in active ▁gen es ▁(" turn ed ▁off ") ▁are ▁generally ▁more ▁cond ensed ▁and ▁associated ▁with ▁struct ural ▁prote ins ▁in ▁heter och rom atin . ▁Ep igen etic ▁modification ▁of ▁the ▁struct ural ▁prote ins ▁in ▁chrom atin ▁via ▁m eth yl ation ▁and ▁ac et yl ation ▁also ▁al ters ▁local ▁chrom atin ▁structure ▁and ▁therefore ▁gene ▁expression . ▁The ▁structure ▁of ▁chrom atin ▁networks ▁is ▁currently ▁poor ly ▁understood ▁and ▁remains ▁an ▁active ▁area ▁of ▁research ▁in ▁mole cular ▁bi ology . ▁ ▁Dynamic ▁chrom atin ▁structure ▁and ▁hierarchy ▁ ▁Ch rom atin ▁under go es ▁various ▁struct ural ▁changes ▁during ▁a ▁cell ▁cycle . ▁Hist one ▁prote ins ▁are ▁the ▁basic ▁pack er ▁and ▁arr anger ▁of ▁chrom atin ▁and ▁can