Red Herring Magazine
Looking for Madam Tetrachromat - Do mutant females walk among us?
By Glenn Zorpette
>From the December 04, 2000 issue
"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.
Full text:http://www.redherring.com/mag/issue86/mag-mutant-86.html
Jeff Nagelbush
[EMAIL PROTECTED]
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