Practice question

Epigenetic regulation in stem cells involves heritable changes in gene activity without altering DNA sequence, primarily through chromatin remodeling, histone modifications, and DNA methylation dynamics. Bivalent domains bearing both H3K4me3 activating and H3K27me3 repressive marks keep developmental promoters poised in embryonic stem cells for rapid activation. Upon lineage commitment, Polycomb repressive complexes resolve bivalency, DNA methyltransferases silence pluripotency loci like Oct4 promoter, and histone deacetylases condense chromatin, restricting potency toward multipotent and unipotent states while preserving genomic integrity and preventing aberrant transposition.