The American Type Culture Collection (ATCC) now provides purified DNA from some of its well-characterized and authenticated cell lines, microbial strains and molecularly cloned viruses. This high-quality DNA has been isolated under aseptic conditions to prevent cross-contamination. Batches are evaluated for integrity, purity and quality by several methods, including agarose gel electrophoresis, ectrophotometry, restriction digestion and suitability for amplification by PCR