Over the past two decades many individual research groups have used groundbreaking molecular biology techniques to search for mutations in genes that are likely candidates for a variety of diseases.

Genome-wide association studies (GWAS) are a powerful method for identifying disease susceptibility genes for common diseases, offering the promise of novel targets for therapeutic intervention that act on the root cause of disease. GWAS involve scanning thousands of samples, either as case-control cohorts or in family trios, utilizing hundreds of thousands of SNP markers located throughout the human genome. Statistical Algorithms are applied that compare the frequencies of either single SNP alleles, genotypes, or multimarker haplotypes between disease and control cohorts.

This analysis identifies regions (loci) with statistically significant differences in allele or genotype frequencies between cases and controls, pointing to their role in disease.

By scanning the genomes of thousands of people and comparing the sick with the healthy, biologists are uncovering markers for DNA sequences they believe clearly increase the risk of type 2 diabetes, cancer, heart disease, inflammatory bowel disease, and other debilitating ailments.

What do all these discoveries mean for medicine?
Predictive testing will have value in cases in which effective preventative interventions exist, and when modest changes in risk improve clinical decision-making.

For many scientists, interest focuses not only on risk assessment but also on a longer-term clinical application: better understanding diseases and designing improved treatments to combat them.

Please refer to these pages for more detail:
Guilt beyond a reasonable doubt
Human genetics: Variants in common diseases
Human Genome-Wide Association Studies
GENOME-WIDE ASSOCIATION:
Closing the Net on Common Disease Genes