Tyramide signal amplification (TSA)-FISH applied to mapping PCR-labeled probes less than 1 kb in size

Tyramide signal amplification (TSA)-FISH was used to map one mouse and two human DNA probes of less than 1 kb in size. The two human probes were 319 a nd 608 bp, and the mouse probe was 855 bp. Probes, made from PCR products, were labeled by incorporating biotin-11-dUTP (human) and biotin-16-dUTP (mo use) during PCR amplification. Signals were readily observed in both interp hase and metaphase cells following TSA-FISH for all three genes, whereas co nventional FISH experiments produced no signals. The two human ATP-binding cassette (ABC) genes, EST883227 (GenBank(R) Accession No. AA243820) and EST 990006 (GenBank Accession No. AA348546), mapped to human chromosomes 7p21 a nd 17q25. The mouse gene, c-myc (exon 2) mapped to band D2 of mouse chromos ome 15. These findings demonstrate the ability of this technique to map sma ll probes (PCR products and expressed sequence tags) of less han 1 kb throu gh highly increased signal amplification.