A Higher Order of Silence

During the development of multicellular organisms, a single fertilized egg gives rise to a plethora of specialized cell types, which are the building blocks of distinct tissues. Because virtually all the cells in the human body contain an identical genome, it is the discriminative reading of all genetic information that determines whether a cell is a muscle, skin, or nerve cell. Mohd-Sarip and Verrijer highlight two studies that provide intriguing new insights into how the regulated compaction of genomic DNA into chromatin is fundamental to keeping a gene turned "on" in one cell lineage but turned "off" in another.