An Introduction to genomics, GWAS, DNA sequencing, and disease-associated variants
Updated: Feb 2
l the cells in our bodies and living organisms contain DNA, the genetic material that determines many factors about the health, function, and characteristics of those organisms and cells. Genomics is a field of study that involves studying all the genetic material of particular organisms or cell types to understand the underlying genetic conditions of those organisms. In the human context, genomics is the study of how the DNA in some or all of our cells affects some of the biophysical characteristics we exhibit or the diseases we may have.
One of the most exciting developments in the field of genomics in the last few decades has been the development of next-generation sequencing technologies such as DNA sequencing, which allows us to ‘read’ the whole genome of organisms . This has allowed for the sequencing of millions of genomes from thousands of organisms and cell types [1,2]. In 2003, the first complete human genome sequence was published . Since then, hundreds of thousands of human genomes have been sequenced, allowing us the ability to do large-scale, whole-genome studies of human populations .
Genome-wide association studies, or GWAS, are studies that involve studying variants, or changes to a genomic sequence at a particular point in the genetic sequence and linking it to a particular characteristic such as the presence of a disease. For example, if we were interested in understanding what genes might be involved in the development of a particular disease, such as asthma, we would sequence the genomes of a large population of humans who had asthma. We would perhaps control for certain factors such as geography, and then take samples in a uniform way across the whole population group being studies. These samples would then be sequenced using DNA sequencing, and then bioinformatic tools can be used to determine whether there are particular variants, or changes in DNA sequence, that are seen more often statistically in those patients with asthma than people without asthma (we already have the genomes of humans without asthma through large sequencing databases). This is the main idea behind GWAS.
If it is found that particular variants or mutations show up in a population with a particular disease, these are termed disease-associated variants. These variants may increase the risk of having a particular disease. Not all diseases will have these genetic variants, as some diseases develop through different mechanisms that don’t involve genetic mutations, however, genetic variant data can often give us important clues about what might be happening biologically to cause particular diseases
1. Genomics Education Programme. 2021. What is genomics? - Genomics Education Programme. [online] Available at: https://www.genomicseducation.hee.nhs.uk/education/core-concepts/what-is-genomics/
2. Ebi.ac.uk. 2021. What is genomics? | Functional genomics I. [online] Available at: https://www.ebi.ac.uk/training-beta/online/courses/functional-genomics-i-introduction-and-design/what-is-genomics/.
3. Genome.gov. 2021. Genome-Wide Association Studies Fact Sheet. [online] Available at: https://www.genome.gov/about-genomics/fact-sheets/Genome-Wide-Association-Studies-Fact-Sheet.
Figure taken from: https://www.genome.gov/sites/default/files/inline-images/DNA_sequencing_Fact-sheet2020-2.jpg