A team around TAN Zheng from the CAS Institute of Zoology has found that single nucleotide variations (SNVs) in human genomes interact with DNA motifs that can form four-stranded secondary structures called G-quadruplexes (G4s). Such interactions result in millions of potential changes in secondary structures in the DNA of human genomes. As most of these changes occur within genes and are enriched near transcription start sites, the finding implies a new and “personalized” mechanism for gene regulation.