The　accurate　detection　of　cancer-related　genes　is　of　great　significance　for　early　diagnosis　and　targeted　therapy　of　cancer.　In　this　contribution,　an　automatically　cycling　operation　of　a　functional　overhang-containing　molecular　beacon　(OMB)-based　sensing　system　was　proposed　to　perform　amplification　detection　of　the　p53　gene.　Contrary　to　the　common　molecular　beacon　(MB),　a　target　DNA　is　designated　to　hybridize　with　a　label-free　recognition　probe　(RP)　with　a　hairpin　structure　rather　than　OMB.　In　the　presence　of　a　target　DNA　of　interest,　the　locked　primer　in　RP　opens　and　triggers　the　subsequent　amplification　procedures.　The　newly-developed　OMB　is　not　only　capable　of　accomplishing　cyclical　nucleic　acid　strand-displacement　polymerization　(CNDP)　with　the　help　of　polymerase　and　nicking　endonuclease,　but　is　also　cleaved　by　restriction　endonucleases,　removing　the　quencher　away　from　the　fluorophore.　Thus,　the　target　DNA　at　an　extremely　low　concentration　is　expected　to　generate　a　considerable　amount　of　double-stranded　and　cleaved　OMBs,　and　the　quenched　fluorescence　is　completely　restored,　leading　to　a　dramatic　increase　in　fluorescence　intensity.　Utilizing　this　sensing　platform,　the　target　gene　can　be　detected　down　to　8.2　pM　in　a　homogeneous　way,　and　a　linear　response　range　of　0.01　to　150　nM　could　be　obtained.　More　strikingly,　the　mutant　genes　can　be　easily　distinguished　from　the　wild-type　ones.　The　proof-of-concept　demonstrations　reported　herein　are　expected　to　promote　the　development　of　DNA　biosensing　systems,　showing　great　potential　in　basic　research　and　clinical　diagnosis.　©　2016　The　Royal　Society　of　Chemistry.