Sometimes, SNPs within a haplotype block can aid in finding a gene responsible for certain diseases – like hemophilia. To track down such genes, researchers can conduct population studies. For example, genome-wide association studies, or GWAS, are carried out to associate specific genetic variations with a disease. In this approach, researchers use two large study groups: people with the disease of interest and a similar group of people without the disease. DNA samples from each study participant are isolated and sequenced before the genomes are scanned for SNPs. If certain SNPs appear more frequently in individuals with the disease as compared to the healthy individuals, then those SNPs are said to be associated with the disease. While it is possible that these SNPs are causing the condition, it is more likely that they are part of a haplotype block that may contain the causal variant.