Editing Chromosome (section)

=== Interphase chromatin ===
The packaging of DNA into nucleosomes causes a 10 nanometer fibre which may further condense up to 30&nbsp;nm fibres.<ref name="Cooper-2019" /> Most of the euchromatin in interphase nuclei appears to be in the form of 30-nm fibers.<ref name="Cooper-2019" /> Chromatin structure is the more decondensed state, i.e. the 10-nm conformation allows transcription.<ref name="Cooper-2019" />

[[File:Heterochromatin vs. euchromatin.svg|thumb|Heterochromatin vs. euchromatin|upright=1.8]]

During [[interphase]] (the period of the [[cell cycle]] where the cell is not dividing), two types of chromatin can be distinguished:
* [[Euchromatin]], which consists of DNA that is active, e.g., being expressed as protein.
* [[Heterochromatin]], which consists of mostly inactive DNA. It seems to serve structural purposes during the chromosomal stages. Heterochromatin can be further distinguished into two types:
** ''Constitutive heterochromatin'', which is never expressed. It is located around the centromere and usually contains [[repeated sequence (DNA)|repetitive sequences]].
** ''Facultative heterochromatin'', which is sometimes expressed.