pathoscribe

Written by Kirsten Batitay | Art by Anoushka Pandya

The sequencing of DNA–determining the specific sequence of bases in DNA–is incredibly useful in the medical field, and Sanger sequencing has been the technology widely used to do this for quite a long time. However, it only sequences one DNA fragment at a time, whereas next-generation sequencing can sequence DNA or RNA a hundred, thousand, or even a million genes in a short time. 

Next-generation sequencing, or NGS, involves various steps: DNA fragmentation, library preparation, massive parallel sequencing, bioinformatics analysis, and variant annotation and interpretation. The first step, DNA fragmentation, breaks the target DNA into shorter segments and is followed by library preparation, the process by which the segments are modified so that each sample can be uniquely identified and the one that enables massive parallel sequencing. One of the most important steps is massive parallel sequencing of the segments using an NGS sequencer, and the information gained from it is then analyzed with bioinformatics software. In this next step, the data is compared to a reference sequence from a human genome to identify any mutations. After this, the segment information is combined to generate results for the full piece of targeted DNA.

The large scope of NGS allows for more accuracy and preciseness in disease diagnosis, classification, and prognoses as therapeutic decision-making. As mentioned, its scope makes it capable of finding new mutations and disease-causing genes and  can be used to find the genetic basis of obscure diseases. This is present especially in pediatrics, a branch of medicine focused on kids, where NGS is currently being used and researched. NGS’ ability to identify mutations also makes it valuable in  cancer treatment and research because tumors are varied and may have multiple mutations in their DNA sequence, which makes it so that they require deeper sequencing. Because of this, targeted panel sequencing is done when using NGS for cancer. Targeted panel sequencing is done for certain diseases or disease categories, where only dozens to hundreds of the genes in these diseases are targeted. In clinical settings, NGS is used to identify high-risk populations for some hereditary cancers and test for mutations in circulating DNA. The latter is called a “liquid biopsy” because many solid tumors shed their DNA, with the DNA winding  up in a patient’s bloodstream or other bodily fluids. This DNA can then be used as a representative sample for tumors. However, further  testing must be done in this application. 

While setting up the required structures and facilities and high staff expertise is a significant disadvantage of NGS, it has incredible potential to be used for precision medicine and personalized cancer treatment. New technologies like next-generation sequencing can undoubtedly become crucial in disease treatment, which is why there is little reason to lose doubt in the various diseases that plague our world today and all the more reason to have hope in the many advancements in the medical and scientific fields.

Works Cited: 

Qin, Dahui. “Next-Generation Sequencing and Its Clinical Application.” Cancer Biology & Medicine, U.S. National Library of Medicine, Feb. 2019, http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6528456/#:~:text=Next%2nd Generation%20 sequencing%20(NGS),a%20short%20period%20of%20time. 

Behjati, Sam, and Patrick S Tarpey. “What Is Next Generation Sequencing?” Archives of Disease in Childhood. Education and Practice Edition, U.S. National Library of Medicine, Dec. 2013, http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3841808/. 

“NGS vs Sanger Sequencing.” Sequencing, http://www.illumina.com/science/technology/next-generation-sequencing/beginners/advantages/ngs-vs-sanger.html#:~:text=The%20 critical%20 difference%20between%20 Sanger,of%20 fragments%20 simultaneously%20 per%20 run. Accessed 25 May 2024. 

“DNA Sequencing.” Genome.Gov, http://www.genome.gov/genetics-glossary/DNA-Sequencing#:~:text=Definition,active%20area%20 of%20 genomics%20research. Accessed 25 May 2024.