DNA sequencing is the process of determining the order of nucleotides (A, C, G, T) in a DNA molecule. Over the years, a number of different decoding DNA technologies have been developed to sequence DNA, each with their own strengths and limitations. In this article, we’ll explore some of the most common DNA sequencing technologies and how they work.
Sanger Sequencing:
Sanger sequencing, also known as chain termination sequencing, is one of the first DNA sequencing technologies that was developed. This method is based on the use of dideoxynucleotides (ddNTPs), which terminate DNA synthesis when incorporated into a growing DNA strand. By using a mixture of normal nucleotides (dNTPs) and ddNTPs, it is possible to generate a series of DNA fragments that differ in length by a single nucleotide. These fragments can then be separated by gel electrophoresis and the order of nucleotides can be determined by reading the sequence of fragments from the smallest to the largest.
Pyrosequencing:
Pyrosequencing is a newer DNA sequencing technology that is based on the detection of light emitted during DNA synthesis. In this method, a single-stranded DNA template is immobilized on a solid support and a series of nucleotides are added sequentially. Each time a nucleotide is incorporated into the growing DNA strand, a chemical reaction occurs that releases a flash of light. The intensity of the light is proportional to the number of nucleotides that are incorporated, allowing the order of nucleotides to be determined.
Illumina Sequencing:
Illumina sequencing is a high-throughput DNA sequencing technology that is widely used today. In this method, DNA fragments are attached to a solid support and amplified using a process called bridge amplification. Next, fluorescently labeled nucleotides are added to the DNA fragments and incorporation is detected using a camera. By repeating this process multiple times, it is possible to generate billions of DNA fragments and determine the order of nucleotides in each fragment.
Ion Torrent Sequencing:
Ion Torrent sequencing is a relatively new DNA sequencing technology that is based on the detection of hydrogen ions that are released during DNA synthesis. In this method, a single-stranded DNA template is attached to a solid support and a series of nucleotides are added sequentially. Each time a nucleotide is incorporated into the growing DNA strand, a hydrogen ion is released, which can be detected by a pH-sensitive electrode. By measuring the changes in pH, the order of nucleotides can be determined.
PacBio Sequencing:
PacBio sequencing is a newer DNA sequencing technology that is based on the detection of light emitted during DNA synthesis. In this method, a single-stranded DNA template is immobilized on a solid support and a polymerase is used to synthesize a complementary DNA strand. As the DNA is synthesized, a fluorescently labeled nucleotide is incorporated and the light emitted is detected by a camera. By repeating this process multiple times, it is possible to generate a long read of DNA sequence that can be several kilobases in length.
Decoding DNA Conclusion
There are a number of different DNA sequencing technologies that are available today, each with their own strengths and limitations. By understanding how these technologies work, it is possible to select the best method for a particular application. Whether you are sequencing a small fragment of DNA or an entire genome, there is a DNA sequencing technology that is right for you.