The Opposite of Three Blind Mice

A bunch of lab mice at the Johns Hopkins School of medicine may be the first of their kind to see in color. Scientist there engineered mice with a human, long-wavelength photo receptor.

How did they know the mice could see colors? Well they didn't really know for sure… but they did prove that the mice could discriminate between lights of various colors, while normal mice couldn’t.

Normal mice railed to discriminate yellow versus red lights when the light intensities were set to give equal activation of their middle wavelength receptor. However, mice with both the human long wavelength and the mouse middle wavelength receptors learned to tell the difference, although it TOOK OVE 10,000 TRIALS TO LEARN TO MAKE THE DISTINCTION.

The emphasis is mine. Scientists are truly patient individuals.

I'm still not sure why they did it except to learn about evolution. The researchers believe the engineered mice mimi how our earliest primate ancestors acquired trichromatic vision (color vision based on three receptors).

At some point in the past, random mutations created a variant of one receptor gene, located on the X chromosome, producing two different receptor types. Present-day New World (South American) monkeys still use this system, which means that in these monkeys only certain females can acquire trichromatic color vision.

Genetic Studies Endow Mice with New Color Vision [press release]

Emergence of Novel Color Vision in Mice Engineered to Express a Human Cone Photopigment[Science (subscription required)]