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 delays of 2-2.5 hours compared to non-carriers.

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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 delays of 2-2.5 hours compared to non-carriers.