The present invention relates to methods and compns. for treating nucleic acids, and in particular, methods and compns. for the detection and characterization of nucleic acid sequences and sequence changes. The invention provides methods for examg. the conformations assumed by single strands of nucleic acid, forming the basis of novel methods of detection of specific nucleic acid sequences. The present invention contemplates use of novel detection methods for, among other uses, clinical diagnostic purposes, including but not limited to the detection and identification of pathogenic organisms. Examples are presented for the analysis of Mycobacterium tuberculosis and hepatitis C virus genes.