Cool tidbit of Science

[LARA]

This is an exceprt from a post on the blog Structure and Strangeness called "The Kaleidescope in our Eyes".    I thought it was cool.

"Color blind is the name we give to people who are only dichromatic, rather than the trichromatic experience that 'normal' people have. This difference is most commonly caused by a genetic mutation that prevents the colorblind retina from producing more than two kinds of photosensitive pigment. As it turns out, most mammals are dichromatic, in roughly the same way that colorblind people are - that is, they have a short-wave pigment (around 400 nm) and a medium-wave pigment (around 500 nm), giving them one channel of color contrast. Humans, and some of our closest primate cousins, are unusual for being trichromatic. So, how did our ancestors shift from being di- to tri-chromatic? For many years, scientists have believed that the gene responsible for our sensitivity in the green part of the spectrum (530 nm) was accidentally duplicated and then diverged slightly, producing a second gene yielding sensitivity to slightly longer wavelengths (560 nm; this is the red-part of the spectrum. Amazingly, the red-pigment differs from the green by only three amino acids, which is somewhere between 3 and 6 mutations).

But, there's a problem with this theory. There's no reason a priori to expect that a mammal with dichromatic vision, who suddenly acquired sensitivity to a third kind of color, would be able to process this information to perceive that color as distinct from the other two. Rather, it might be the case that the animal just perceives this new range of color as being one of the existing color sensations, so, in the case of picking up a red-sensitive pigment, the animal might perceive reds as greens.

As it turns out, though, the mammalian retina and brain are extremely flexible, and in an experiment recently reported in Science, Jeremy Nathans, a neuroscientist at Johns Hopkins, and his colleagues show that a mouse (normally dichromatic, with one pigment being slightly sensitive to ultraviolet, and one being very close to our medium-wave, or green sensitivity) engineered to have the gene for human-style long-wave or red-color sensitivity can in fact perceive red as a distinct color from green. That is, the normally dichromatic retina and brain of the mouse have all the functionality necessary to behave in a trichromatic way. "

Wow.

[SteveS]

Geez - fascinating stuff. That was a really interesting read!  Thanks for sharing.