Do mutant females walk among us?
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From: Peter Langston <psl>
Date: Thu, 7 Dec 100 17:10:44 -0800
Subject: Do mutant females walk among us?
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Looking for Madam Tetrachromat - Do mutant females walk among us?
By Glenn Zorpette
From: the December 4, 2000 issue of Red Herring Magazine
"Oh, everyone knows my color vision is different," chuckles Mrs. M, a
57-year-old English social worker. "People will think things match, but I
can see they don't." What you wouldn't give to see the world through her
deep blue-gray eyes, if only for five minutes.
Preliminary evidence gathered at Cambridge University in 1993 suggests that
this woman is a tetrachromat, perhaps the most remarkable human mutant ever
identified. Most of us have color vision based on three channels; a
tetrachromat has four.
The theoretical possibility of this secret sorority -- genetics dictates
that tetrachromats would all be female -- has intrigued scientists since
it was broached in 1948. Now two scientists, working separately, plan to
search systematically for tetrachromats to determine once and for all
whether they exist and whether they see more colors than the rest of us
do. The scientists are building on a raft of recent findings about the
biology of color vision.
The breakthroughs come just in time. "Computers, color monitors, and the
World Wide Web have made having color blindness a much bigger deal than it
ever was before," says Jay Neitz, a molecular biologist who studies color
vision at the Medical College of Wisconsin in Milwaukee. Color-blind
individuals, he explains, often lose their way while navigating the Web's
thicket of color cues and codes. "Color-blind people complain miserably
about the Web because they can't get the color code," Dr. Neitz says. (Just
try surfing on a monochrome monitor.)
Most people are trichromats, with retinas having three kinds of color
sensors, called cone photopigments -- those for red, green, and blue. The
8 percent of men who are color-blind typically have the cone photopigment
for blue but are either missing one of the other colors, or the men have
them, in effect, for two very slightly different reds or greens. A
tetrachromat would have a fourth cone photopigment, for a color between
red and green.
Besides the philosophical interest in learning something new about
perception, the brain, and the evolution of our species, finding a
tetrachromat would also offer a practical reward. It would prove that the
human nervous system can adapt to new capabilities. Flexibility matters
greatly in a number of scenarios envisaged for gene therapy. For example,
if someone with four kinds of color photopigments cannot see more colors
than others, it would imply that the human nervous system cannot easily
take advantage of genetic interventions.
© 2000 Peter Langston