What is next-generation sequencing (or NGS)?

If you’re considering prenatal genetic testing, such as non-invasive prenatal screening (NIPS), you may be curious about how these tests work. The short answer is that most NIPS tests use next-generation sequencing (NGS) technology to assess a pregnancy’s chance for certain chromosomal conditions – such as Down syndrome, trisomy 18, and trisomy 13. But what exactly IS next-generation sequencing? If you want to dive into the details of genetic sequencing technology, what next-generation sequencing means, and how it can be used to give you information about your pregnancy, this post is for you!

Next-generation sequencing (NGS) is a type of technology used to read (sequence) our genetic code or DNA. But before we get into the details of NGS, let’s talk about why we would want to read the DNA code in the first place. Our DNA is like a recipe book that provides our body with instructions for how to grow and develop, and changes in a person’s DNA impact our body’s development. Therefore, examining a person or a pregnancy’s DNA code through genetic sequencing helps us gain insight into genetic conditions or other developmental differences that could occur as a result of differences in a person or pregnancy’s DNA.

Juno Diagnostics uses next-generation sequencing to process prenatal genetic screens andtests

How does next-generation sequencing work and why is it important? 

NGS is able to sequence (read) many fragments of DNA at once in order to determine what the overall DNA code says. Another name for NGS is “massively-parallel sequencing” because of its ability to sequence many DNA strands at the same time, rather than one at a time, as is the case for other methods, such as Sanger sequencing. 

To understand NGS or massively-parallel sequencing, imagine if all of the pages in a large book had been cut into tiny little pieces of paper. Each slip of paper would contain a few words to a few sentences. If you’re asked to reassemble the book and read what it says., you would need to read through thousands of these paper slips to piece the book together! If you have technology that helps you read many scraps of paper simultaneously, you will be able to figure out what the book says more quickly. As you can imagine, it would be much slower work to examine each slip of paper one at a time, read it, pick up another slip and read it, then another and another, one at a time for thousands of slips of paper, before you have enough information to piece the book together. 

This method of reading many DNA fragments at once (“in parallel”) means NGS is able to increase how quickly we can sequence DNA dramatically. By reducing the time and cost needed to perform genetic testing, NGS has made genetic testing more affordable and accessible to those who need it.  

What is NGS used for? 

There are many applications for next-generation sequencing. Scientists can use this technology to sequence the entire human genome (that is, every single piece of the genetic code) relatively quickly and inexpensively. The more people whose genomes we analyze, the more we learn about human genetics and genetic factors that contribute to disease and development across different populations. NGS can be used to sequence multiple genes at once to look for genetic variants (mutations) linked to cancer, cardiovascular diseases, metabolic syndromes, and more. If someone carries a genetic variant linked to a disease, we have a better chance of finding that variant if we’re able to quickly sequence multiple genes at once, and then that individual can get the resources and care they need.

Here at Juno, we use next-generation sequencing for our Hazel™ Non-invasive Prenatal Screening (NIPS) test. Through NGS, Hazel™ is able to read the code of millions of DNA pieces found in your blood. Many of these pieces come from you, but some pieces also come from your baby’s placenta. By analyzing these DNA fragments, Hazel™ is able to examine the relative amount of DNA in your sample quickly and easily, providing screening for chromosomal conditions in your pregnancy. Hazel™ is performed on a simple blood sample that can be collected from home.

You can read more about Juno’s Hazel™ Non-invasive Prenatal Screening (NIPS) test here

- Authored by Kelly Miller, MS, LCGC | Genetic Counselor 


JunoDx.com and the materials and information it contains are not intended to be and do not constitute medical advice, other health advice, or diagnosis.  Do not use JunoDx.com or the materials and information published at JunoDx.com as a substitute for medical care and treatment. You should always consult with a qualified physician or healthcare provider about your specific circumstances. 

January 10, 2023 — Stephanie McClintock