as map out the mutations. Once they have been mapped out, cloned, and identified, it can be determined whether a mutation represents a new gene or not. These experiments showed that mutations in the rhodopsin gene affected vision and can even cause retinal degeneration in mice. The same amino acid change causes human familial blindness, showing how phenotyping in animals can inform medical diagnostics and possibly therapy. Evolutionary origin of phenotype The RNA world is the hypothesized pre-cellular stage in the evolutionary history of life on earth, in which self-replicating RNA molecules proliferated prior to the evolution of DNA and proteins. The folded three-dimensional physical structure of the first RNA molecule that possessed ribozyme activity promoting replication while avoiding destruction would have been the first phenotype, and the nucleotide sequence of the first self-replicating RNA molecule would have been the original genotype. See also Ecotype Endophenotype Genotype-phenotype distinction Molecular phenotyping Race and genetics References External links Mouse Phenome Database Human Phenotype Ontology Europhenome: Access to raw and annotated mouse phenotype data "Wilhelm Johannsen's Genotype-Phenotype Distinction" by E. Peirson at the Embryo Project Encyclopedia Classical genetics Polymorphism (biology)