Following sequencing of the human genome, many guanine-rich sequences that had the potential to form quadruplexes were discovered. Depending on cell type and cell cycle, mediating factors such as DNA-binding proteins on chromatin, composed of DNA tightly wound around histone proteins, and other environmental conditions and stresses affect the dynamic formation of quadruplexes. For instance, quantitative assessments of the thermodynamics of molecular crowding indicate that the antiparallel g-quadruplex is stabilized by molecular crowding. This effect seems to be mediated by alteration of the hydration of the DNA and its effect on Hoogsteen base pair bonding. These quadruplexes seemed to readily occur at the ends of chromosome. In addition, the propensity of g-quadruplex formation during transcription in RNA sequences with the potential to form mutually exclusive hairpin or G-quadruplex structures depends heavily on the position of the hairpin-forming sequence.