Concept $18\mathrm{.}2$ Eukaryotic gene expression is regulated at many stages

the expression of different genes by cells with the same genome.

any changes to chromatin, i$.$e$.$ histone tails or DNA itself, that alter the accessibility of chromosome regions for transcription

the addition of an acetyl group to an amino acid in a histone tail, which usually promotes transcription by opening up chromatin

Covalent addition of methyl groups to the histone protein tails, which usually inhibits transcription by closing chromatin

Inheritance of traits transmitted by mechanisms not involving the nucleotide sequence itself but rather processes such as chromatin modification