Casper Fish™ Genetics
How can a fish reopen doors long closed to scientific research? The answer is literally skin deep in the fish. Since the 1930s, zebra fish have been a model organism for studying human diseases. The fertilized eggs, embryos, and fry are transparent, allowing scientists to easily observe and study topics such as tumor growth, brain tissue development, and blood vessel growth. However, after a few weeks, transparency declines as their bodies become opaque, limiting the research window for scientists.
For researchers at Children’s Hospital Boston, who were using zebra fish to study the development of cancer in vivo, frustration mounted over the small window of time open to study cancer cells in zebra fish embryos. In response, researchers began crossbreeding specific genetic strains of zebra fish to produce a transparent fish. After a year, they developed the Casper Fish™, which lacks pigment in its skin and scales, and therefore is transparent. The Casper Fish’s transparency allowed researchers to extend their research into the adult stage of this model organism.
Two genes were involved in the development of the Casper Fish™. The mitfa gene controls development of the melanophores, the black pigmented stripes on zebra fish. The nacre allele (n) corresponds to a mutation in the mitfa gene that is present in the Casper Fish™, eliminating the appearance of melanophores. An unnamed gene controls the development of reflective iridophores on zebra fish, and the roy allele (r) corresponds to the mutation exhibited in Casper Fish™ for this gene. To produce a Casper Fish™, both genes must be homozygous recessive mutants (nnrr). Therefore, 2 nacre and 2 roy alleles must be present. Crossbreeding and understanding genetic inheritance allowed for this scientific breakthrough.
Incorporate the genetics
Carolina Biological Supply Company is the exclusive distributor of the Casper Fish™. To bring the excitement of this newly developed model organism into your classroom, we now offer the Carolina™ Genetics of the Casper Fish™ Kit. In this kit, students crossbreed zebra fish males and Casper Fish™ females and observe the embryological development of the F1 generation. This engaging new kit not only allows students to watch cellular division and differentiation, it also incorporates the basics of inheritance. While observing embryological development of the collected transparent embryos, your students construct dihybrid crosses to predict the genotypic and phenotypic frequencies of the F1 and F2 generations. Below is an example of the type question students think through as they observe these growing embryos daily:
Using a Punnett square, calculate the genotypic frequencies of the resulting F1 generation, assuming the parental generation is true breeding (homozygous for both traits). What fraction of the resulting F1 generation would be Casper Fish™?
The Carolina™ Genetics of the Casper Fish™ Kit addresses the following National Science Education Standards for grades 9–12:
- Life Science: The Cell and the Molecular Basis of Inheritance
Allow your students to observe genetics in action with the Casper Fish™. Not only will you meet the standards of your science course, you will also engage and excite your students with science in action.
Read a scientific article about the Casper Fish™: Transparent Adult Zebrafish as a Tool for In Vivo Transplantation Analysis