What is a genome-wide association study (GWAS)?
In genomics, a genome-wide association study (GWA study, or GWAS), is an observational study of a genome-wide set of genetic variants in different individuals to see if any variant is associated with a trait. GWA studies typically focus on associations between single-nucleotide polymorphisms (SNPs) and traits like major human diseases, but can equally be applied to any other genetic variants and any other organisms.

When applied to human data, GWA studies compare the DNA of participants having varying phenotypes for a particular trait or disease. These participants may be people with a disease (cases) and similar people without the disease (controls), or they may be people with different phenotypes for a particular trait, for example blood pressure. This approach is known as phenotype-first, in which the participants are classified first by their clinical manifestation(s), as opposed to genotype-first. Each person gives a sample of DNA, from which millions of genetic variants are read using SNP arrays. If there is significant statistical evidence that one type of the variant (one allele) is more frequent in people with the disease, the variant is said to be associated with the disease. The associated SNPs are then considered to mark a region of the human genome that may influence the risk of disease.

GWA studies investigate the entire genome, in contrast to methods that specifically test a small number of pre-specified genetic regions. Hence, GWAS is a non-candidate-driven approach, in contrast to gene-specific candidate-driven studies. GWA studies identify SNPs and other variants in DNA associated with a disease, but they cannot on their own specify which genes are causal.

The first successful GWAS published in 2002 studied myocardial infarction. This study design was then implemented in the landmark GWA 2005 study investigating patients with age-related macular degeneration, and found two SNPs with significantly altered allele frequency compared to healthy controls. As of 2017, over 3,000 human GWA studies have examined over 1,800 diseases and traits, and thousands of SNP associations have been found. Except in the case of rare genetic diseases, these associations are very weak, but while they may not explain much of the risk, they provide insight into genes and pathways that can be important.
O que é um estudo de associação em todo o genoma (GWAS)?
Em genômica, um estudo de associação em todo o genoma (estudo GWAS), é um estudo observacional de um conjunto de variantes genéticas em diferentes indivíduos para ver se uma variante está associada a uma característica. Os estudos GWA geralmente se concentram em associações entre polimorfismo de nucleotídeos únicos (SNPWA) e características como doenças humanas principais, mas podem ser aplicados igualmente a qualquer outra variante genética e a qualquer outro organismo. Quando aplicados a dados humanos, os estudos GWA comparam o DNA de participantes com diferentes fenótipos de uma determinada característica ou doença. Esses participantes podem ser pessoas com uma doença específica (casos) e pessoas semelhantes sem a doença (controlo), ou podem ser pessoas com diferentes fenótipos para uma determinada variante, por exemplo, pressão arterial.