🚀 go-pugleaf

In article <9t9blc$16s$1@slb7.atl.mindspring.net>,
Jonathan W. Hendry <j_hendry@ix.netcom.com> wrote:
>
>"Vishal Dhokia" <vishal@ddhokia.fsnet.co.uk> wrote in message
>news:9t87q5$mmh$1@newsg1.svr.pol.co.uk...
>> What would be the consequence of having an extra type of cone that is
>> sensitive to EM radiation in the nonvisible spectrum e.g UV light ?  Would
>> we perceive a "new" colour?
>
>I recall reading about a woman with extra color sensitivity, not that
>long ago. I thought it was on the BBC web site, but I haven't been
>able to find the story there.

In one form of red-green color blindness there is a modified visual 
pigment.  Since this form is sex-linked, a woman heterozygous for the
trait will have both forms, hence 4 rather than 3 visual pigments.
Since areas in which one X chromosome or the other is active are
distributed like the colors in a tortoiseshell cat, the woman you
read about may have had mostly one form in one eye and mostly the other 
in the other eye.

Mammals are pretty limited in color vision compared to other vertebrates,
probably because our ancestors were little burrowing nocturnal critters
during most of mammalian history, and just made it out into the sunlight
when the dinosaurs got wiped out.  Many birds have 7 visual pigments, and
many reptiles and fish have much better color vision than we do.  Many
diurnal lizards show different behaviour when UV light is available.

The human retina can detect near-UV, but these wavelengths are absorbed
by the lens.  People who have had the lens removed due to cataracts can
perceive these wavelengths.  I asked a friend about it and he said there
was some difference after his cataract surgery but he couldn't really
describe it.