Acid treatment of Drosophila deoxyribonucleic acid.

In cytologic preparations of chromosomes, acid-treated deoxyribonucleic acid (DNA) is found largely in the native state. However, acid treatments widely used for chromosome preparations produce significant amounts of depurination in DNA. DNA is similarly sensitive to depurination in intact cells or as purified DNA. If treated with alkali, these apurinic gaps can be converted to single strand breaks. Acid treatment has widely different effects on specific fractions of DNA. In Drosophila melanogaster 3% of the DNA is composed of very long tracts of pyrimidines (polypyrimidines) which are resistant to acid hydrolysis. The implications of these results for molecular cytogenetics are discussed.