Epigenetics: heritable changes in gene expression without DNA sequence changes. DNA methylation: 5-methylcytosine (5mC) at CpG sites. CpG islands: promoter regions with high CpG density — methylation → silencing. DNMT1 (maintenance), DNMT3a/3b (de novo). TET enzymes: oxidize 5mC → 5hmC → demethylation. Histone modifications: H3K4me3 (active promoters), H3K27me3 (repression, Polycomb), H3K9me3 (heterochromatin), H3K27ac (active enhancers). Histone acetyltransferases (HATs) vs deacetylases...
- epigenetics
- genomics
- biology