linkage analysis is just the first step to gene identification, since it only provides a probable chromosomal location of gene(s) influencing the phenotypic trait. Single-nucleotide polymorphisms (SNPs) offer an opportunity to test for association between the beta EEG traits and SNP located in the GABA receptor genes on chromosome 4. Subsequent linkage disequilibrium analyses of 69 SNPs within a cluster of four GABA(A) receptor genes performed by the same group found significant associations with both beta oscillations and alcoholism, yet, no coding differences were found between the high-risk and low-risk haplotypes, suggesting that the effect is mediated through gene regulation (Edenberg et al., 2004).
