Which mammals contain genes that will some day enhance human senses?
Although mice, like most mammals, typically view the world with a limited color palette – similar to what some people with red-green color blindness see – scientists have now transformed their vision by introducing a single human gene into a mouse chromosome. The human gene codes for a light sensor that mice do not normally possess, and its insertion allowed the mice to distinguish colors as never before.
In a study published in the March 23, 2007, issue of the journal Science, Howard Hughes Medical Institute researchers at Johns Hopkins, together with researchers at the University of California at Santa Barbara, demonstrated in a series of cleverly designed color vision tests that the genetic modification allows mice to see and distinguish among a broader spectrum of light waves. The experiments were designed to determine whether the brains of the genetically altered mice could efficiently process sensory information from the new photoreceptors in their eyes. Among mammals, this more complex type of color vision has only been observed in primates, and therefore the brains of mice did not need to evolve to make these discriminations.
The new abilities of the genetically engineered mice indicate that the mammalian brain possesses a flexibility that permits a nearly instantaneous upgrade in the complexity of color vision, say the study’s senior authors, Gerald Jacobs and Jeremy Nathans.
While this study used a human gene in mice I think it has implications for human upgrades. Imagine a future in which some people genetically engineer their offspring to see a much wider range of colors. Instead of eye cone cells with 3 absorption peaks for light frequencies imagine 10 different variations on cone cells with 10 different peak absorption frequencies for light.
Or how about hearing? Imagine a human with the ability to hear up into much higher frequencies of sound. We could use genes from dogs or other mammals to enhance us for greater ability to distinguish sounds just as these scientists created mice with a human gene to give them greater ability to see colors.
Update: Humans and some Old World primates are the only mammals that can see 3 colors.
Retinas of primates such as humans and monkeys are unique among mammals in that they have three visual receptors that absorb short (blue), medium (green) and long (red) wavelengths of light. Mice, like other mammals, only have two; one for short and one for medium wavelengths.
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Nathans suggests that these knock-in mice mimic 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.
In contrast, among Old World (African) primates such as humans, the two different X chromosome genes duplicated so that each X chromosome now carries the genes for both receptor types, giving both males and females trichromatic color vision.
Imagine you were going to genetically engineer the perfect dog (I expect people will some day). Well, wouldn't you want to give him greater ability to see colors?
By Randall Parker at 2007 March 22 11:07 PM Transhumans Posthumans | TrackBackThis is just cool... and wouldn't I like to see into the near-UV and near-IR regions...
Or four-color vision like some women.
Robert Silvetz,
Thanks for that. I had no idea that tetrachromat women exist who can see 4 colors. From that link:
Dr. Neitz, who conducts his research with his wife Maureen, said only women have the potential for super color vision.That's because the genes for the pigments in green and red cones lie on the X chromosome, and only women have two X chromosomes, creating the opportunity for one type of red cone to be activated on one X chromosome and the other type of red cone on the other one. In a few cases, women may have two distinct green cones on either X chromosome.
But it's unlikely, Dr. Neitz said, that all of the women with four types of color cones will have the potential for superior color vision, because for many, their two red cones will be so close to each other in the wavelengths they detect that they won't see things much differently than a three-color person does.
He estimated that 2 percent to 3 percent of the world's women may have the kind of fourth cone that lies smack between the standard red and green cones, which could give them a colossal range.
But it would be possible for a woman to have both variations of the pigment on the same gene. It would work by duplication of the gene during replication so it has two copies. Then one copy could mutate to shift to a different frequency. Now, maybe that doesn't exist in humans. But it could be made to exist using genetic engineering.
But before they pat themselves on the back for their superior evolution, he said, it's important to note that humans are just getting back to where birds, amphibians and reptiles have been for eons.Those creatures have long had four-color vision, but a key difference is that their fourth type of color detector is in the high-frequency ultraviolet range, beyond where humans can see.
It turns out the males of some species really do have brighter plumage than the females but us humans just can't see it.
Combine the bird pigment and the mutated human pigment and we could make humans (or dogs for that matter) who could see 5 different colors.
5 color vision approximates out to 10^10th colors... Egads...
I recall the eye encodes color into dark/light, red/green, yellow/blue before sending it over the optical nerve to the brain. Adding a fourth color is easy, it lets you substitute a true yellow instead of red+green=yellow. But adding a fifth or further color would require more interesting rewiring.
On the other hand, the mice probably had dark/light, red/green to start with. I don't know where they'd fit in an extra color receptor. But apparently they did.