The zebrafish is an important model organism in human genetics and developmental biology because, like humans, it is a vertebrate, and it is genetically very similar to humans. 70% of the genes that are associated with disease in humans have functional homologs in zebrafish. In the laboratory, most genetic manipulations to this fish can instantly be observed because its larvae are transparent. In comparison to rats as a model system, zebrafish are easier to rear and produce more offspring. Zebrafish are currently being used as a model in research on cancer, multiple sclerosis, infectious diseases and many other human diseases.