explain the molecular basis of the intracellular process (within cells of the scn) that entrains the circadian clock to a strict 24-hour cycle. include the following words in your explanation: scn, per, cry, clock, cycle, dimer, complex, nucleus, glutamate, intracellular cascade, light, mrgcs, expression, enhances, inhibits, increased, decreased, degradation, 24-hours, dna, and entrains.
