The goal of this proposal is to develop an in vivo mutagenicity assay based on transgenic fish. The transgene to be incorporated is a lambda phage shuttle vector with a lac I target gene that has demonstrated sensitivity to mutagens. After exposing fish to suspected mutagens, the vector is rescued from fish genomic DNA with lambda phage packaging extracts. Subsequent infection of E. coli, allows mutations to be visually scored by blue/white color selection of plaques, formed on an E. coli lawn. Small species of fish have been used extensively in evaluating carcinogenicity of test compounds, and have shown themselves to be useful in identifying human carcinogens prior to rodent bioassay. Therefore, a fish-based mutagenicity assay will allow a more in-depth evaluation of suspected mutagens by extending multiple species testing. However, unlike current rodent bioassays, a fish-based mutagenicity assay will also allow in-depth evaluation of mutagens contaminating aquatic ecosystems and open new avenues of testing compounds prior to release into the environment. In addition, the ability to visualize embryonic development combined with the ready supply of large numbers of fertilized eggs will allow this assay to be adapted to analyzing mutagenic-potential of teratogens. During phase I the feasibility of constructing transgenic fish will be explored; In phase II, the system will undergo further development by producing high copy fish and initial testing of mutagens.