Nucleic acid hybridization of highly repeated DNA in extracts of single Drosophila

We have developed and characterized a method for the rapid detection and quantitation of specific DNAs in partially purified extracts of single Drosophila. While the method should be applicable to a number of repetitious DNA sequences, we have used the polypyrimidine DNA sequences (TCTCT)n to develop this technique. Using hydroxyapatite chromatography, we were able to measure the amount of nucleic acid hybrid formed and to obtain a thermal elution profile of the hybrid formed in extracts of single flies. Under a variety of conditions, purified DNA and DNA in partially purified extracts gave essentially identical results. The procedure can be used to detect the presence of rare sequences, or to measure the relative abundance of a prevalent DNA species. 40 different wild type strains of Drosophila melanogaster were examined using this technique and all contain similar amounts of the same polypyrimidine/polypurine sequence. From a small scale screening of different laboratory stocks of D. melanogaster, a variant was found which formed more DNA-DNA hybrid with labelled polypyrimidine tracts than did wild type. The additional hybrid was distinguished by a lower thermal stability than the hybrid formed in wild type.