Genes for photoreceptor proteins in cones

The gene for the blue receptor is autosomal; the
genes for the red and green receptors are X
chromosomal. The absorption spectra of the
three receptors show maxima of 426 nm for
blue, about 530 for green, and about 550 for red.
The red receptorwas discovered to be polymorphic,
with two somewhat different absorption
maxima at 552 and 557 nm.