Middle Wavelength Sensitive Photopigment Gene Expression is Absent in Deuteranomalous Colour Vision

The deutan-type colour vision deficiencies, deuteranopia, and deuteranomaly are the most common types of colour blindness. A known cause of deutan colour vision defects is the loss of genes encoding the middle wavelength sensitive (M) photopigments. Deutan defects have also been found to be associated with a deleterious point mutation in the M photopigment genes. This chapter tests the hypothesis that M gene expression is absent in all commonly occurring deutan defects. It shows that the commonly occurring deutan defects in which individuals have normal appearing M genes, are caused by a failure to express M pigment. Moreover, it appears that the failure is likely to be complete.