What are epigenetic modifications?

the addition of reversible changes to histone proteins and DNA

the removal of nucleosomes from the DNA

the addition of more nucleosomes to the DNA

mutation of the DNA sequence

This are epigenetic modification: a, b and c. (changes on histones, removal and nucleosomes formation.

Explanation:

Histone modification is a key step in genomic regulation. Activation of histones leads DNA to form new nucleosomes, which low transcription levels in this zone.

On the other hand, deactivation of histones removes those nucleosomes, permitting DNA to be transcripted.

The addition of more nucleosomes to the DNA.