A biosensing system was developed to accurately detect a single nucleotide change in the target organism genome, integrating a selective isothermal amplification and a sensitive dendron-mediated DNA hybridization assay in the array format. The novelty arises from the coupling reactions of the dendron and its use as a crosslinker. The allele-specific probes were oligonucleotide-dendron conjugates prepared by fast and clean click-chemistry (thiol-yne reaction) and coupled onto the photo-activated surface of polycarbonate substrates (carbodiimide reaction). The output was forest-array chips with multipoint-site crosslinkers and compatible with current microarray fabrication technologies. The products of blocked recombinase polymerase amplification (blocked RPA), formed at 37 °C, were hybridized with attached probes for specific nucleotide genotyping. The developed approach exhibited sensitive recognition of DNA variants compared to chips based on linear crosslinkers (10-100 fold), showing excellent analytical performances for planar chip and fluidic formats. The methodology was successfully applied to detect the H1047R mutation in the PIK3CA gene (c.3140A > G) from clinical samples of human cancer tissues, the results being consistent with sequencing techniques. The colorimetric biosensing method was reliable, versatile, low cost, sensitive (detection limit genomic DNA: 0.02 ng μL-1), and specific (accuracy >95%).