Single Gene Gives Mice Three-Color Vision 184
maynard writes "A study in the peer-reviewed journal Science shows that mice transgenetically altered with a single human gene are then able to see in full tri-color vision. Mice without this alteration are normally colorblind. The scientists speculate that mammalian brains even from animals that have never evolved color vision are flexible enough to interpret new color-sense information with just the simple addition of new photoreceptors. Such a result is also indicated by a dominant X chromosome mutation that allows for quad-color vision in some women." A sidebar in the article includes a nice illustration of what two-color vs. three-color mice might perceive.
Re:Question I couldn't get from the article (Score:4, Informative)
Re:Martian colours (Score:3, Informative)
Synesthaesia is the blending of senses, such that (e.g.) hearing a certain sound may trigger the sensation of taste or colour. In this case, the guy couldn't actually see the "missing" colours (via his eyes) at all. Yet he could "experience" the sensation of those colours via his synesthaesia.
Re:Could people handle four-color vision? (Score:1, Informative)
Yes, people (more specifically: women) exist with four-color vision and they do just fine.
Re:possible use in humans? (Score:1, Informative)
Re:True colour (Score:5, Informative)
This doesn't make any sense. Red cones are not sensitive to blue light. Here is a diagram [utah.edu] showing the sensitivities of of the three cones (S, M, and L or Blue, Green and Red) in our retina whose signals combine to create color.
Our perception of color comes from the combination and comparison of the stimulation of three different cones, each maximally sensitive to different wavelengths. The output of the cones gets combined in what are called opponent pathways, one is Red-Green, and the other is Blue-yellow. The Red-Green pathway compares the output of the Red and Green cones and the Blue-yellow pathway compares the output of the blue cone with the sum of the red and green cones. This is why you will never see a color that is reddish-green or blueish-yellow (see nick) at least in the additive sense that red+blue=violet and yellow+blue+green.
So why does extremely short wavelength light appear to contain a reddish component? I don't believe that anyone knows the answer to that yet. But the hypothesis is that somewhere along the path from cone to cortex the input from a blue cone and red cone combine which turns our perception of an extremely short wavelength light into a combination of short wavelength light (blue) and extremely long wavelength light (red). So our sensation of color becomes a continuum that loops back on itself as opposed to our sense of pitch (which is also frequency or wavelength).
Interestingly people who have had their lenses removed are somewhat able to perceive ultraviolet light. This is because the lens ordinarily blocks UV light and blue cones are sensitive to UV light but very little ever penetrates to the retina normally. Apparently they see it as lilac.
Many mammals, fish, birds, insects, and reptiles (basically everyone except us) are able to see UV light as well. It's a good that we can't for two reason. One is that there is more chromatic aberration at shorter wavelengths. Basically blue light bends more than red light. This makes focusing more difficult. Also, more importantly, UV light damages DNA which is a very, very, bad thing. This [handprint.com] is a good resource for learning more.
Yes and no (Score:5, Informative)
Yes.
It depends off your target site, but yes it is possible.
- You can replace bone marrow (remove a mutated one that led to cancer, and put another one (given from a relative) that is exempt of the broken gene that lead to the cancer). As you are modifying stem cells (blood cells precursors) the modification is rather permanent. And as the newly produced white blood cells are always re-trained after creation they won't consider your body as foreign so you won't have immune system rejection (graft vs. hosts in this case). And as a bonus, because bone marrow cells have homing capabilities, they're as easy as a blood transfer to inject. But the problem is that, during the time between when you radiated the old marrow to kill the cancer and when the newly injected one has finished recreating white cells, there's a window during which the organism is defenseless against infections.
- Viruses are small things that basically work by injecting their genetic information (DNA or RNA) inside a host cell. Scientist can assemble small virus like things that use the virus shell and thus are able to inject their material, but inside they contain the gene you need to add for the therapy. As far as I've heard there were attempt to use such a system to treat mucoviscidosis (by injecting a gene to help produce working chloride channels). It is administered as a spray. The problems are (beside the high cost of such a method) that the spray only reach the supperficial layer of cells in the bronchus. These are differenciated cells that don't multiply anymore, they only do their work until they die off and fall out. The precursors are deeper and not affected by the therapy. Thus the effects aren't permanent. Plus, after some time the hosts immune system ends up discovering those modified virus and/or infected cells, considers them as foreign and develops antibodies against them. Thus the therapy gets ineffective after some times. Thus the whole idea was scrped and now we mostly use drugs that are cheaper, makes the cells work using the gene they already had before (other ion channels - carbocystein) or directly dilutes the secretions (acetylcystein), and whose effect doesn't diminish with time (thus they are much more effective at reducing the speed of degradations of lungs and buying time before lung transplantation gets necessary).
No. /before/ the brain and the retina gets wired. The colour perception capabilities develops when the nervous fibres grow and connect to different population of receptors.
Transgenic mice = before birth gene modification.
For the mutation to work, it has to happen
You can't 'cure' colour-blindness with gene therapy alone.
Technically speaking, there are virus that can infect retina before birth. But they would be much more difficult and expensive to produce, plus they can have bad side effects, and they are harder to control if they did inject their genes. Also the whole stuff is less ethical for the poor mice. Right now, you modify the mice at the stage of either zygote (1 single cell) or not-yet feconded gamete. You let the zygote do a couple of division, you get one of the dozen cell and check it the gene is still in place. If it is, you implant the stuff in a mother mouse. With the virus way, you have to inject the virus into a mother mouse while she still carries the baby mice (and hope that there won't be too much side effects - inflamation and such - for the mother or the mice she carries), then once the baby mice are born, you have to screen them to see which one carry the new gene (and has them into the eyes. The virus can target several organs, and won't necessarily infect the mice's eyes. I don't know, but maybe removing one of the eyes could be the only solut
Re:Question I couldn't get from the article (Score:5, Informative)
Don't thank god for that, thank natural selection. A virus that impairs its host's vision is not going to get much time to reproduce itself.
Re:Women only? (Score:2, Informative)
That gene in a male would distort color perception but the male would still end up with only 3 types of cones. They would have a partial colorblindness. They would be an anomoly, as they would be able to see part of the spectrum the missing cone should be able to see, but not all of it. (More common colorblindness is caused by a mutation in which one type of cone simply does not work.)
At least That is what I understand based on the information in TFA.
Re:True colour (Score:1, Informative)
Btw, google for "hyperspectral imaging". Cameras that take pictures in more than three frequency bands.