This invention describes a nucleic acid testing procedure in a form of portable device or a test kit for the purposes of clinical genetic testing, infectious disease diagnostics, biodefense, forensic analysis, paternity testing, pet and cattle breeding, food testing, etc. This testing does not include toxic chemicals and is simple enough to be used by an average individual without any special laboratory training. The procedure includes collecting the sample, potential isothermal amplification of the whole genomic DNA or a fragment of genomic DNA, denaturing double-stranded DNA into single-stranded form, hybridizing the denatured sample DNA to single-stranded allele-specific tester oligonucleotides complementary to the analyzed DNA sequence of interest, selective removal of single-stranded DNA from DNA hybrids, and finally detecting the label in double-stranded hybrids to determine the presence or absence of a particular sequence in the initial sample.