Your Query returns 4 Accession Numbers:

Query TermAccessionNCBI TaxonidSynonymsPhenotype (OMIM) *
MAPKK1NM_00892710090Mek1    MEKK1    Prkmk1    Map2k1   
MAPKK1NM_0027559606MEK1    MKK1    PRKMK1    MAP2K1   
MAPKK1BC05475410090Map2k1   
mapkk1AF3918084577

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

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Text2Knowledge ... Yong Huang 2002