Heterochromatin's a tightly packed form of DNA. Its major characteristic's that transcription's limited. As such, it's a means to control gene expression, through regulation of the transcription initiation. Structure Chromatin's found in two varieties: euchromatin and heterochromatin. Originally, the two forms were distinguished cytologically by how intensely they stained - the euchromatin's less intense, while heterochromatin stains intensely, indicating tighter packing. Heterochromatin's usual… (More on Heterochromatin)