Any approach to genetic investigation that aims to find the function for some known protein or gene. It contrasts with the more traditional forward genetics approach, in which an unknown gene is sought for a known function (identified by the effect of a mutation). For example, analysis of gene sequences reveals open reading frames, which are the hallmarks of functional genes (see reading frame). Reverse genetics methods can be used to discover the function of such genes. For example, the gene can be cloned, subjected to mutation, and then reinserted into the organism (e.g. a bacterium or yeast cell) to see what effect the mutation has on function. A similar approach can be taken starting with a protein of unknown function. The amino-acid sequence can be back-translated into genetic code, a DNA probe constructed for part of the DNA sequence, and the relevant gene selected from a DNA library of the organism.