Epidermal growth factor receptor
Transheterozygotes are useful in the study of genetic interactions. An example from Drosophila research: the wing vein phenotype of a recessive mutation in the Epidermal growth factor receptor (Egfr), a gene required for communication between cells, can be dominantly enhanced by a recessive mutation in Notch, another cell-signalling gene. A transheterozygote between Egfr and Notch has the genotype "Notch/+ ; Egfr/+" (where "Notch" and "Egfr" represent mutant alleles, and + represents wildtype alleles). The dominant interaction between Egfr and Notch suggested that the Egfr and Notch signalling pathways act together within the cell to affect the pattern of veins in the fly's wings.