An improved method for in situ nick translation of human chromosomes with biotin 11-labelled dUTP detected by biotinylated alkaline phosphatase.

Nick translation of the DNA of conventionally prepared human metaphase chromosomes using DNase I and biotin dUTP combined with streptavidin-phosphatase-detection assay produced a banding-like appearance. This pattern seems to be due to differences in DNase I sensitivity along the chromosomes. The Y chromosome could be clearly distinguished from the other chromosomes because of its intensely dark labelled heterochromatic region. In addition to DNase I concentration, hypotonic treatment seems to be an important methodological factor influencing band resolution. Together with recently published similar methods these results indicate that in situ nick translation using biotinylated nucleotides may develop into a useful technique to overcome several problems of human cytogenetics.