Figure 1

Genetic tools can be subdivided into two groups depending on the research question. Forward genetic approaches begin with a specified human disease phenotype. Animals displaying similar symptoms can be used to identify genetic elements underlying these disease traits by selective breeding and molecular biological techniques, such as linkage analyses. Both naturally occurring genetic variation and artificially induced variation can be used to score disease phenotypes. Alternatively, reverse genetic approaches are based on systematically mutating known genes to determine their role in human physiology and pathology by analyzing the phenotypic effects. ENU, N-ethyl-N-nitrosourea; ESC, embryonic stem cell; iPSC, induced pluripotent stem cell; HR, homologous recombination; ZFN, zinc-finger nuclease.