Methods and apparatus for DNA sequencing

The present invention provides a method and apparatus for automated DNA sequencing. The method of the invention includes the steps of: a) using a processive exonuclease to cleave from a single DNA strand the next available single nucleotide on the strand; b) transporting the single nucleotide away from the DNA strand; c) incorporating the single nucleotide in a fluorescence-enhancing matrix; d) irradiating the single nucleotide to cause it to fluoresce; e) detecting the fluorescence; f) identifying the single nucleotide by its fluorescence; and g) repeating steps a) to f) indefinitely (e.g., until the DNA strand is fully cleaved or until a desired length of the DNA is sequenced). The apparatus of the invention includes a cleaving station for the extraction of DNA from cells and the separation of single nucleotides from the DNA; a transport system to separate the single nucleotide from the DNA and incorporate the single nucleotide in a fluorescence-enhancing matrix; and a detection station for the irradiation, detection and identification of the single nucleotides. The nucleotides are advantageously detected by irradiating the nucleotides with a laser to stimulate their natural fluorescence, detecting the fluorescence spectrum and matching the detected spectrum with that previously recorded for the four nucleotides in order to identify the specific nucleotide.