It has been suggested that gene duplication facilitates the evolution of developmental innovations, and vertebrates possess multiple copies of genes probably present in single copies in their chordate ancestors. To investigate mechanisms of vertebrate genome evolution, we are mapping cloned zebrafish genes and comparing the results to mammalian gene maps.
Analysis shows large chromosome segments conserved among species.
At least four copies of some paralogous chromosome segments exist in zebrafish, and they generally correspond to orthologous chromosome segments in mammals, suggesting that two polyploidization events occurred prior to the divergence of fish and mammal lineages. Comparative genomics suggests the content of chromosomes in the last common ancestor before polyploidization. The zebrafish gene map will facilitate molecular identification of mutated zebrafish genes, which can suggest functions for human genes known only by sequence.