Your Query returns 2 Accession Numbers:

Query TermAccessionNCBI TaxonidSynonymsPhenotype (OMIM) *
dperiodNC_0043547227Clk    PER    dPER    clk-6    CG2647    EG:155E2.4   
dperiodNM_0803177227Clk    PER    dPER    clk-6    CG2647    EG:155E2.4   

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* OMIM link based on symbol match for human and mouse.

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Text2Knowledge ... Yong Huang 2002