DNA sequencing is a technique used to determine the exact sequence of nucleotides in a DNA sample. Electrophoresis, a method for separating DNA fragments, is used when the DNA differs in length by only one base. DNA samples are placed in a gel and exposed to an electric field.
Automatic sequencing machines read electrophoresis gels, resulting in faster and more accurate DNA sequencing. These machines can produce a rough draft of a DNA sequence of 20,000 to 50,000 bases in a few hours. First-generation DNA sequencing technology employed the Maxam-Gilbert method and the Sanger method. Finishing is a method that involves the final assembly of the raw sequences that come out of the sequencing machines. Newer sequencing technologies have made it possible to sequence the genomes of several organisms, including the mouse, the rat, a malaria-carrying mosquito and mustard weed.
Scientists can use sequence information to determine which sections of DNA contain genes. Scientists can analyze those genes for mutations that may cause disease. The sequencing of the human genome has given scientists a blueprint of the human being, allowing them to find answers for complex biological processes, including how a baby forms from a single cell, how the human brain works, and how genes regulate tissue and organ functions.