Sequence variations, such as polymorphisms, are detected by detecting differences between or among melting profiles of plural nucleic acids. Melting profiles are produced by observing the nucleic acids during a temperature change over a period of time. If the nucleic acids are diluted into solutions for analysis, the nucleic acid concentrations between or among the solutions can be substantially the same. The melting profiles and sequence variation can be used to identify changes in a wild-type nucleic acid sequence, such as a single-nucleotide polymorphism (SNP), a small insertion or deletion, or a small inversion.