Professor Charalambos Kyriacou, from the University of Leicester, has identified a mutant gene that can drastically change the dynamics of a dinner party. While one gene may put guests to sleep before dessert, another could keep them chatting until the early hours of the morning. This is due to the fact that circadian rhythms, which regulate the sleep-wake cycle and other body functions, can be affected by abnormal genes. Chronobiologists have defined these different sleep patterns as "advanced sleep phase syndrome" or the "lark phenotype" for those who are early to bed and rise early and "delayed sleep phase syndrome" or the "owl phenotype" for those who rarely go to bed before the small hours of the morning but struggle with early mornings.
Studies have shown that circadian rhythms are organised by cells known as the suprachiasmatic nuclei (SCN), located in the hypothalamus, which regulate basic body drives such as hunger, thirst, and sexual desire. Our internal clocks tend to lose track of time, and as a result, the cells use external cues to reset twice a day. However, in the absence of external cues, "free-running" cell experiments have revealed a 25-hour rhythm, gradually drifting out of sync with the natural environment.
The molecular clock involves three teams of genes. The first two initiate each cycle, and these involve a combination of genes known as clock, cycle, cry, and per. These proteins interact to influence the period of each cycle. The tug of war between cry and per creates a period, with the per protein activating the next cycle. The final team interacts with the cycle to create other effects. These include the doubletime gene, which reduces the period, and the timeless gene, which resets the clock at dawn and dusk.
The sequencing of the human genome has led to the discovery of clock genes in humans, with three per genes, one more cry gene, and additional genes resembling doubletime present. Various mutations in these genes have been linked to the "lark" and "owl" phenotypes. The knowledge gained from this research has many applications, including chronotherapy for conditions such as jet lag and shift work. With a greater understanding of these genes and other associated factors, treatments can be developed that have broad applications, including the prevention of transport disasters and surgical malpractice and the slowing down of the ageing processes that impact peripheral clocks in other organs.