Novel disposable electrochemical DNA sensors were prepared for the detection of a target DNA sequence on the p53 tumor suppressor (TP53) gene. The electrochemical platform consisted of screen-printed carbon electrodes (SPCEs) functionalized with a water-soluble reduced graphene oxide-carboxymethylcellulose (rGO-CMC) hybrid nanomaterial. Two different configurations involving hairpin specific capture probes of different length covalently immobilized through carbodiimide chemistry on the surface of rGO-CMC-modified SPCEs were implemented and compared. Upon hybridization, a streptavidin-peroxidase (Strep-HRP) conjugate was employed as an electrochemical indicator. Hybridization was monitored by recording the amperometric responses measured at -0.10 V (vs an Ag pseudo-reference electrode) upon the addition of 3,3',5,5'-tetramethylbenzidine (TMB) as a redox mediator and H2O2 as an enzyme substrate. The implemented DNA platforms allow single nucleotide polymorphism (SNP) discrimination in cDNAs from human breast cancer cell lines, which makes such platforms excellent as new diagnosis tools in clinical analysis.