In order to investigate how loss- and gain-of-function alleles of the same locus might lead to analogous phenotypes, Drosophila geneticists created transgenic flies that harbor the mutations found in the majority of individuals with LEOPARD syndrome {Y279C and T468M of the PTPN11 gene [corkscrew (csw) in Drosophila]} to create humanized models of LEOPARD syndrome. Here, PTPN11 is linked to Noonan syndrome with multiple lentigines.