SNPs are very common variations scattered throughout the genome. Because they are fairly easy to measure and are also remarkably stable, being inherited from generation to generation, they have become useful as gene "markers." If a particular SNP is located near a gene, then every time that gene is passed from parent to child, the SNP is passed on also. This enables researchers to assume that when they find the same SNP in a group of individual genomes, the associated gene is present also.