Tetrachromatism is the ability to see four basic colors in place of the standard three -
red,
green and
blue. While the existance of Tetrachromatists has not been confirmed yet, Dr. Neitz and Dr. Jordan are both conducting studies and are trying to find people with this
disorder. Due to the
genetics of vision, these people must be female and chances are that their male children will be
color-blind.
Why is this so? The genes for green and red photopigments are found on the X chromosome, that for blue is located far off on another chromosome. Since men only have only one X chromosome, no error-checking occurs when the new X chromosome is created in the egg. Since the red and green pigments are located so proximally they somtimes cross over; some of the eggs are disadvantaged from the start. The X chromosome might lack either a red or green photopigment gene or have dual red/green photopigment genes - regardless, the male offspring is bound to be color-blind.
However, if the lucky sperm cell enriches the egg with another X chromosome and a phenomenon called X inactivation occurs, there is the possibility of a Tetrachromatist. Through X inactivation, all four pigment-genes would be activated and the woman would have receptors for Red, Green, Off-green (or Off-red) and blue color vision.
Jeremy Nathans, a pioneer in color-vision research at Johns Hopkins University School of Medicine postulates that the brain would be able to interpret the fourth signal without trouble and assign it a new 'color.' The true determining aspect for seeing the fourth color is the degree of seperation between the peak in sensitivity for the new pigment versus red or green - if the peaks are too close, the person might only see a different (although alien) shade of green or red. Possible advantages of this would include increased awareness of skin tones (see if a child is bleak or flushed, even to a small degree;) the universal knowledge of a fourth color could aid in categorization and general awareness - try to imagine life without one of the three primaries.
So there is a color we're not seeing. Has anyone else read up on this, could it be perceived through biochemical manipulation? Since all the actual interpretation and assigning of a color takes place in the mind, this should be possible... too bad they can't tell us what the new color looks like, this is slowly driving me insane =)