Neitz M, Kraft T W, Neitz J
Department of Ophthalmology, Medical College of Wisconsin, Milwaukee 53226-4812, USA.
Vision Res. 1998 Nov;38(21):3221-5. doi: 10.1016/s0042-6989(98)00076-5.
Spectral subtypes of L pigment are produced by a serine/alanine dimorphism at amino acid position 180. X-chromosomes that carry genes for the different subtypes occur with about equal frequency in normal men. Females have two X-chromosomes: thus, about 50% of women will inherit genes for both L pigment subtypes, although on different X-chromosomes. In these women, X-inactivation is expected to produce about equal numbers of LS180 and LA180 cones in addition to middle (M) and short (S) wavelength-sensitive cones to total four spectrally distinct cone types. Consistent with this expectation we found nearly equal expression of genes for two spectrally distinct subtypes of L pigment in five of nine female retinas examined.
