What are the possible roles of proteins in histone modification?

What general role does acetylation of histone protein amino acids play in the transcription of eukaryotic genes?

What parts of the genome are reversibly methylated? How does this affect gene expression?

Identical twins each carry the same genome, but over time, can develop different phenotypes. How can you explain this?

What are the roles of the Polycomb and Trithorax complexes in eukaryotic gene regulation?

Describe how reversible chemical changes to DNA and histones are linked to chromatin modification.

Why are changes in nucleosome spacing important in changing gene expression?