BigDyeTerminators

BigDye Terminator technology refers to a specific type of fluorescent dye used in DNA sequencing. Developed by Applied Biosystems (now part of Thermo Fisher Scientific), these dyes are incorporated into the DNA strands during the Sanger sequencing process. Each of the four standard DNA bases (Adenine, Guanine, Cytosine, and Thymine) is labeled with a distinct fluorescent dye, allowing for their identification based on the color of fluorescence emitted when excited by a laser.

The process involves a chain termination reaction. DNA polymerase extends a primer along a template strand, but the reaction is supplemented with dideoxynucleotides (ddNTPs). These ddNTPs lack the 3'-hydroxyl group necessary for further elongation. When a ddNTP is incorporated into the growing DNA strand, the chain terminates. Each ddNTP is labeled with a BigDye Terminator. Therefore, a mixture of terminated DNA fragments of varying lengths is generated, with each fragment ending in a base labeled with a specific colored dye.

Following the sequencing reaction, the mixture of fluorescently labeled fragments is separated by size, typically using capillary electrophoresis. As the fragments pass a detector, the laser excites the fluorescent dyes, and the emitted light is recorded. The order of the emitted colors corresponds to the sequence of the DNA. BigDye Terminators have been a cornerstone of automated Sanger sequencing, enabling high-throughput and reliable DNA analysis for decades in research, diagnostics, and forensic applications.