|Abstract:|| Gene and genome duplications, which increase gene copy number at different scales, are considered to be important contributors to the evolution of organisms. During the evolution of vertebrates, two successive rounds of whole genome duplication, called 1R and 2R have highly influenced the organization of gene content of genomes. After WGDs, genomes returned progressively to a diploid state, but a certain amount of genes were kept as duplicates, which led to the formation and extension of many gene families. A fish-specific genome duplication called 3R occurred at the base of the teleost fish lineage. A fourth round of WGD has also been characterized in the Salmonidae. Examples of gene family expansion in vertebrates will be presented.