Zebrafish

Several characteristics favor the choice of zebrafish for genetic research. First, zebrafish are easy to maintain in large numbers in a small laboratory space. Second, their generation time is relatively short: three months. Finally, females produce large clutches of offspring, about 50 to 100 a week. The zebrafish also presents advantages for embryological analysis: Its embryos develop externally, and are largely transparent for the first 36 hours of development.

The first proponents of the zebrafish model, George Streisinger and his colleagues at the University of Oregon, outlined its genetic characteristics and provided a thorough description of zebrafish embryogenesis. Zebrafish research entered a new phase when two groups, at the University of Tuebingen (Germany), and at Harvard Medical School, performed large-scale chemical mutagenesis experiments and isolated nearly 2,000 mutations that affect almost every aspect of embryonic development, from gastrulation to axonal pathfinding. Once the mutations were identified, they were studied to determine their developmental effects, after which their genetic and molecular nature was analyzed. These early genetic studies in zebrafish were limited by the lack of genomic resources, such as maps of the genome or genomic libraries, but these deficiencies were gradually eliminated during the late 1990s. Zebrafish research has entered a new phase since the completion of the genome project. This effort provided the sequence of the entire zebrafish genome and made cloning of zebrafish genes much more efficient.