Abstract
Approximately 10% of genes oscillate according to a circadian clock. Even though cells are capable of independent oscillation there is a master controller in the brain, the suprachiasmatic nucleus (SCN), that provides a coordinated response throughout the body, influenced by daily and seasonal patterns of light and heat. These genes have widely varied functions but are significantly influential in DNA damage repair, the cell cycle, cellular proliferation and apoptosis, as well as metabolic function. Normal circadian rhythms are essential for the body’s natural defence against disease and cancer. Deregulation may enhance the capacity for carcinogenesis in the skin and the influence of the circadian clock helps explain two of the anomalies of melanoma exposure patterns: A higher incidence amongst indoor as opposed to outdoor workers and on intermittently as opposed chronically exposed skin.