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The developing zebrafish is transparent, making it an ideal subject for the study of development.

embryogenesis development of the embryo from a fertilized egg histological related to tissues including humans, both in the general body plan and in specific organs. Close parallels exist in many aspects of early embryogenesis and in the anatomical and histological features of the brain, spinal cord, sensory systems, cardiovascular system, and other organs. Not infrequently, genetic defects in zebrafish resemble human disorders. Owing to these similarities, zebrafish genetics is being broadly applied to address both basic biological questions and to model human inherited diseases.

mutagenesis creation of mutations gastrulation embryonic stage at which primitive gut is formed

Useful Traits for Researchers

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 Tue-bingen (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.

transgenics transfer of genes from one organism into another

Ongoing Research Involving Zebrafish

Zebrafish research continues at a fast pace. New rounds of mutation identification are in progress. To supplement chemical mutagenesis, retroviral vectors were developed as mutagenic agents and applied on a large scale. Tools to study the functions of individual genes, such as transgenics, were

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