List core circadian clock genes.
['PER1, CRY1, CRY2, CLOCK, BMAL1, and CKlε ', ' Expression levels of five clock genes (Rev-Erbα, Per1, Per2, Bmal1 and Cry1)', 'altered expression patterns of the circadian clock genes, Bmal1 and Per2. ', 'This review will focus on the core circadian clock genes CLOCK, BMAL1, Per, and Cry.', 'CLOCK, RORA, and NPAS2', 'Rev-erbα and Bmal1 ', 'he core circadian clock genes BMAL1, PER1/2 and CRY1/2.', 'CLOCK/BMAL1, the core circadian clock components']
['The core circadian clock genes are CLOCK, BMAL1, Per, and Cry.']
['CLOCK', 'BMAL1', 'Per', 'Cry', 'CKlε']