What is GWAS?¶
A genome-wide association study (GWAS) is an approach that involves rapidly scanning single nucleotide polymorphisms (SNPs) across entire genomes of many people to find genetic variation associated with a particular disease. Once new genetic associations for a disease are identified, researchers can gain new insights into the biological mechanisms underlying the disease, and use the information to develop better strategies to detect, treat and prevent the disease. Such studies are particularly useful in finding genetic variations that contribute to common, complex diseases, such as asthma, cancer, diabetes, heart disease and mental illnesses.
GWAS is also laying the groundwork for the era of personalized medicine in which the current one size-fits-all approach to medical care will give way to more customized strategies. As genome-wide scans become cheaper and more efficient, health professionals can use such tools to provide patients with individualized information about their risks of developing certain diseases. The information will enable health professionals to tailor prevention programs to each person's unique genetic makeup. In addition, if a patient does become ill, the information can be used to select the treatments most likely to be effective and least likely to cause adverse reactions in that particular patient.
GWAS identify associations between SNPs and phenotypic traits by identifying systematic trends in allele frequency variation as a function of phenotypic variation. Technological advancements allow investigation of the impact of large numbers of SNPs distributed throughout the genome.
How is it conducted?¶
- Researchers identify two groups: one group of people with a disease condition (patients) and one group of healthy individuals (controls).
- Then DNA samples are collected from patients and control individuals (e.g. via blood or cheek swabs). The extracted DNA is sequenced using whole genome sequencing techniques.
- Next, genomes of diseased individuals are compared to the genomes of non-diseased individuals. If certain genetic variations are found to be significantly more frequent in people with the disease compared to people without disease, the variations are said to be "associated" with the disease.
- The associated genetic variations can serve as powerful pointers to the region of the human genome where the disease-causing problem resides. However, the associated variants themselves may not directly cause the disease. For example, you may find multiple SNPs in a region that are equally well correlated with liver disease, but that only one of those SNPs causes the phenotype. It is also common to find that none of the correlated SNPs are causative, rather they all are just tightly linked to an undetected mutation and are "tagging along" with the actual causal variants.
- Design, Analysis, and Interpretation of Genome-Wide Association Scans (Statistics for Biology and Health) by Daniel O. Stam
- Genome-Wide Association Studies: From Polymorphism to Personalized Medicine by Krishnarao Appasani
- GWAS Wiki
- About GWAS on the know genetics website