Sensitive and high resolution in situ hybridization to human chromosomes using biotin labelled probes: assignment of the human thymocyte CD1 antigen genes to chromosome 1.

A method for in situ hybridization originally developed for mapping genes in the nematode, Caenorhabditis elegans has been adapted for high resolution cytological mapping of genes in the human. The probe DNAs are labelled by incorporation of biotin dUTP and the site of hybridization detected by immunofluorescence. For the accurate assignment of the hybridization signal to chromosome bands, visualized by staining with Hoechst 33258, a heterologous ribosomal DNA probe is also included in the hybridization reaction. These rDNA signals are used as fiducial markers when aligning the two fluorescent images. We demonstrate the method by assignment of the human thymocyte CD1 antigen genes to human chromosome 1q22-23.