Fish Growth Hormone Genes: Structure and Divergence

This review provides information on the structure of growth hormone genes (GHGs) in fish and the divergence of coding, intron, and adjacent flanking regions; original data obtained in our laboratory are also considered. In most fish species, GHGs are represented by a single copy, while some taxonomic groups have two paralogous genes. The coding sequences of GHGs are conserved. Gene length variations depend on the length of non-coding and flanking regions and introns. The divergence rate of gene sequences varies not only between different taxonomic groups, but also in the time of divergence within groups. In flanking regions, only the regulatory elements are conserved.