Some people may stay up late and have trouble waking in the morning due to a CRY1 gene mutation which alters the human circadian clock. Carriers of the gene variant (frequency of up to 0.6% in human genetics databases) experienced nighttime sleep del

A dominant mutation in the human circadian clock gene CRY1 has been linked to familial delayed sleep phase disorder (DSPD), which causes a delay in sleep timing aligned with "night owl" behavior. This mutation enhances CRY1’s function as a transcriptional inhibitor, lengthening the molecular circadian rhythm and disrupting normal sleep patterns. The variant is relatively common, affecting up to 0.6% of the population, and is associated with delayed and fragmented sleep in carriers. This discovery provides a genetic basis for DSPD, a disorder previously lacking clear molecular explanations.