Efforts to discover chromosomal regions, and ultimately genes associated with a specific phenotype or disease like nicotine dependence, can utilize linkage analysis. Genes located near each other on the same chromosome will likely be inherited together. Linkage analysis assesses the presence of a phenotype in large, high-risk families, with the goal of determining the location of the gene responsible for the phenotype in relation to a known genetic marker. Linkage analysis studies can be very useful in identifying the location of a susceptibility disease gene, but there are several limitations. Largely, the results of linkage analyses of nicotine dependence have not been consistently replicated by more than two independent studies and there is a great deal of variability in the measures that are used to assess nicotine dependence (Han et al. 2010; Li 2008). However, of the 13 regions on 11 chromosomes that have been identified in nicotine dependence linkage analyses, regions on chromosomes 9, 10, 11, and 17 have been detected by the greatest number of studies; chromosomes 1, 5, 10, 11, 12, 16, 20, and 22 have also
