The present invention provides methods of obtaining structural information about a biopolymer sample. The methods include labeling portions of a biopolymer, such as DNA or RNA, linearizing the biopolymer in some cases, and determining the distance between the labels. The user can then compare different samples' between-label distances to qualitatively compare different samples and to assay a given sample for additions or deletions of nucleotides in the regions flanked by the labels. The methods also permit sequencing of biopolymers.