Researchers have added genes to the genomes of lab mice that are "blueprints"
for a class of color receptors unique to primates, such as humans, apes, and monkeys.
With their new genes, some of the mice passed tests showing they were able to
see in
"full color," trichromatic vision. Normally mice see a muted array of grays,
blues, and yellows.
The findings hint that mammal brains (including our own) are extremely
adaptable—readyto process inputs they didn't even know existed.
The study also raises the possibility that color vision as we know it could have
arisen from a single mutation.
(Related: "New Mouse Teeth, Whiskers Grown From Handful of Cells" [February 26,
2007].)
New Visual Realm
Trichromacy depends on three types of photoreceptor cells in the eye, which
absorb light at different wavelengths.
For example, short-wavelength receptors are most sensitive to blues,
medium-wavelength receptors are most sensitive to greens, and long-wavelength receptors are most
sensitive to reds.
When light hits the receptors, the brain compares their responses to perceive
color.
Normally, nonprimate mammals see with dichromatic color vision, because their
brains contain receptors only for short and medium wavelengths. This makes most mammals
somewhat color-blind, relative to primates.
The new study is by Gerald Jacobs of the University of California, Santa
Barbara, and
colleagues at Johns Hopkins School of Medicine and Howard Hughes Medical
Institute, both in Baltimore, Maryland. The findings will be published in tomorrow's issue
of the journal Science.
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