A graphene-based electrochemical DNA sensor has been developed for the low-concentration detection of breast cancer-related BRCA1 gene. The DNA sensor used a "sandwich" detection strategy, in which capture probe (DNA-c) and reporter probe (DNA-r) DNAs hybridize to target probe DNA (DNA-t) in a sandwich arrangement on a graphene-modified glassy carbon electrode (GCE). The DNA-r was conjugated to gold nanoparticle and the oxidation of gold nanoparticle was used for the electrochemical detection of DNA-t. The sensor performance was monitored with cyclic voltammetry (CV) and chronoamperometry. The sensor was found to be stable, reproducible and sensitive and it could detect up to 1 femtomolar BRCA1 gene (5.896 femtogram/ml). {\textcopyright} 2014 Elsevier B.V.