A technique for amplifying the quantity of specific sequences of nucleic acid in a specimen. The patient’s DNA, or specimens thought to contain pathogenic DNA, are mixed with DNA ligase and oligonucleotide probes. Double-stranded DNA is denatured. Probes bind to the complementary strands on any denatured target DNA. Ligase joins the bound probes, and multiple copies of the DNA of interest are made. In clinical practice, ligase chain reactions are used primarily in urinary (noninvasive) assays to detect genital infections with chlamydia or gonorrhea.