Your Query returns 3 Accession Numbers:

Query TermAccessionNCBI TaxonidSynonymsPhenotype (OMIM) *
B2ARBC0124819606ADRB2R    ADRBR    BAR    ADRB2   
B2ARNM_0000249606BAR    ADRBR    ADRB2R    BETA2AR    ADRB2   
B2ARL389059544

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

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Text2Knowledge ... Yong Huang 2002