Answer:
Repression of gene expression
Explanation:
Heterochromatin is formed by highly-packed DNA regions. A functional consequence of heterochromatin formation is that these regions become inaccessible to transcription factors, thereby inhibiting gene transcription (genes in these regions are 'switched off'). Heterochromatin is formed by epigenetic modifications added to histone tails that form nucleosomes, i.e., histones H2A, H2B, H3 and H4. The epigenetic marks include, among others, acetylation and methylation.