GNAT2 encodes the cone version of α-transducin (Morris and Fong, 1993), and mutations in GNAT2 result in complete achromatopsia – i.e. no cone function at all (Kohl et al., 2002) – incomplete achromatopsia or extreme red-green color blindness (protanopia) (Rosenberg et al., 2004). The gene discussed is GNAT2; the disease is red-green color blindness.