Chemically-induced genetic damage in fish: Isolation and characterization of the dab (Limanda limanda) ras gene

Polycyclic aromatic hydrocarbons (PAHs) have been implicated in the aetiology of carcinogenesis in fish liver. In mammalian models, such compounds cause characteristic DNA mutations at codons 12, 13 and 61 of the ras gene, leading to oncogene activation. In this report, the isolation and characterization of the normal ras gene of the North Sea flatfish dab (Limanda limanda) is described. Two ras genes have been identified using polymerase chain reaction (PCR) which showed extensive sequence homology to other fish and mammalian ras gene counterparts. The sequence information reported here will enable the subsequent identification of mutated dab ras alleles in feral fish taken from areas of high PAH contamination in the North Sea, and from fish exposed experimentally to specific PAHs under controlled laboratory conditions.