Day 083 - Genetic upgrades

Submitted by Sam on 11 August, 2011 - 23:19

Colour blindness, or the inability to distinguish between certain colour combinations, can either be acquired or inherited, and affects about 8% of males and 0.5% of females in some way. It is one of the most common and best understood genetic anomalies, having first been self-diagnosed over two-hundred years ago by chemist John Dalton.

Non-colour blind people are trichromats; they possess three different photopigments sensitive to three different wavelengths of the visible spectrum in the photoreceptive cells of their eyes. Individuals with inherited colour blindness cannot express all three of these photopigments in their eyes and therefore are sensitive to only a limited range of the spectrum. In the most common form of colour-blindness the lack of a single pigment leads to a difficulty in distinguishing between red and green. Less common forms of colour blindess include monochromats, those lacking the genes for two pigments, and anchromatopsic people, those lacking all three pigments, and who can only see in black and white.

Experiments with mammals – from mice to primates – have demonstrated that colour vision can be conferred through gene-therapy. Genes encoding for the production of the previously missing photopigment have been delivered to colour-blind animals through a specially modified virus vector, injected directly into the back of the eye. Once expressed, the treated animals gain the full complement of pigments, and gain full colour vision, as tested by various behavioural tests. This therapy has brought full colour vision to animals that have never had it before; male squirrel monkeys are naturally dichromatic, and therefore have difficulty in distinguishing between certain shades of red and green. Following the gene therapy to confer the human photopigment gene, the monkeys exhibited behaviour consistent with trichromatic vision: their vision and perception of the world had been upgraded.

Whilst there has been success in curing colour blindness in animals, there are currently no clinical trials planned for humans. This is largely because colour blindness is considered a mild disability, and the procedure to cure it carries risks of eye infection potentially much greater than the benefits it brings. However, the success of the treatment in introducing new colour ranges to primates suggests that our own brains will also be able to adapt to new colour ranges. This has the rather profound consequence that one day it may just be possible to add an additional receptor to our eyes using gene therapy which will upgrade our vision so that we could see ultraviolet light, like bees do. With one more pigment, we could add yet another colour to our perceptual palette and would be able to share the pentachromatic world of Papilio butterflies.

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