Summary
Scan many genomes for variants statistically linked to a trait or disease.
In depth
GWAS compare allele frequencies at hundreds of thousands to millions of SNPs between cases and controls. Statistical thresholds are strict (p < 5×10^-8) to avoid false positives. Hits are usually in non-coding regions and each has small effect.
Polygenic risk scores combine many variants.
A GWAS tests each SNP in turn, assuming that nearby variants are inherited together, so the signal marks a region (a haplotype block) rather than the causal variant. Results are shown on a Manhattan plot, where peaks above the significance line mark loci. Thousands of loci are known for height, schizophrenia, type 2 diabetes and many others.
Limitations include the small effect of each variant, the need for very large samples (hundreds of thousands), confounding by ancestry, and poor transferability to groups under-represented in studies, since most participants have been of European ancestry. Follow-up uses fine mapping and functional experiments.
Example: a GWAS identified variants in the complement factor H gene as a major risk factor for age-related macular degeneration, giving new insights into the disease.
Frequently asked questions
What is Genome-Wide Association Studies?
Scan many genomes for variants statistically linked to a trait or disease.
Which area of biology covers Genome-Wide Association Studies, and how advanced is it?
Genome-Wide Association Studies is one of the 54 topics in Genetics. It is rated Advanced, so it suits learners who want specialist depth. Related topics in this area include Polygenic Inheritance, Quantitative Trait Loci, Population Genetics Models.
Can you give an example of Genome-Wide Association Studies?
GWAS identified the complement factor H variant in age-related macular degeneration.
What should I learn before Genome-Wide Association Studies?
Work through the Beginner topics in Genetics first, such as Heredity, Gene, Allele, then return to Genome-Wide Association Studies. Advanced topics assume the Intermediate vocabulary.
What topics are related to Genome-Wide Association Studies?
The closest topics to Genome-Wide Association Studies are Polygenic Inheritance, Quantitative Trait Loci, Population Genetics Models, Epigenetics. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Genome-Wide Association Studies?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Genome-Wide Association Studies. To practise the whole of Genetics, use the Genetics quiz.
How is Genome-Wide Association Studies different from Polygenic Inheritance?
Genome-Wide Association Studies: Scan many genomes for variants statistically linked to a trait or disease. Polygenic Inheritance: A trait controlled by many genes producing continuous variation, such as height and skin colour. Read both side by side and note what each one explains.
How should I study Genome-Wide Association Studies step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Polygenic Inheritance and explain the difference aloud. Finally, take the Genetics quiz and come back to this page for any question you miss.