 In most organisms, constitutive heterochromatin occurs around the chromosome centromere and near telomeres.The regions of DNA packaged in facultative heterochromatin will not be consistent between the cell types within a species, and thus a sequence in one cell that is packaged in facultative heterochromatin (and the genes within are poorly expressed) may be packaged in euchromatin in another cell (and the genes within are no longer silenced).However, the formation of facultative heterochromatin is regulated, and is often associated with morphogenesis or differentiation.