Sequencing several genomes, including that of the zebra fish, has revealed a num

Question

Sequencing several genomes, including that of the zebra fish, has revealed a number of receptors and transporters. In one case, positional cloning of the zebra fish golden gene identified a putative cation exchange protein called SLC24A5. When the golden gene is mutated, the normally black horizontal stripes are pale or golden in appearance because the amount of black pigment or melanin is greatly reduced. Design an experiment to identify where the protein encoded by the golden gene is expressed and localized in the zebra fish. What is the term used when a mutant gene and its phenotype, for instance golden in zebra fish, is rescued by expressing an orthologous gene from another animal?

Explanation / Answer

Forward-genetics approaches.

To generate mutants, male fish are exposed to themutagen ethylnitrosourea (ENU), which typically induces pointmutations. Zebrafish are relatively resistant to ENU toxicity,allowing higher levels of mutagenesis and specific locus hit ratesthan can be achieved with other vertebratemodels.Random mutagenesis hasalso been successfully carried out in zebrafish using retroviralmethods. Although lower in efficiency thanchemical mutagens, this method has the advantage of tagging eachinsertion event, greatlyfacilitating theidentification of the mutated gene and circumventing the laboriouspositional cloning that is required with other forward-geneticapproaches.

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