Characterization of polypyrimidines in Drosophila and L-cell DNA

Unusually long pyrimidine tracts (polypyrimidines), ranging from 100 to over 1000 nucleotides in length, have been found in Drosophila melanogaster DNA. They are compared to shorter pyrimidine tracts (25-150 nucleotides) which have previously been found in L-cell DNA. Both species were able to anneal to homologous DNA; Drosophila polypyrimidines formed stable hybrids while L-cell polypyrimidines formed hybrids of lower thermal stability. In both cases, the kinetics of the reaction was rapid, suggesting that these tracts are part of highly repeated DNA.