Genetics as it applies to evolution, molecular biology, and medical aspects.
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I recently had my eyes checked and discovered that I have unilateral red-green color blindness in my left eye (I'm male). Using both my eyes, I can see colors perfectly, but when I close my right eye the reds and greens turn to burnt-orange. I never really noticed it because I'm always using both eyes. Here is my question... Being unilateral, is the inheritance pattern of my color blindness still X-linked recessive? If not, then what's its transmission pattern or etiology? I'm not sure, but I'm thinking that it is not X-linked recessive because my cells in my right eye are not expressing the trait. Please help.
i think there may have been some postfertilisation modification of your DNA during your development from zygote to individual. no idea what exactly thoguh... Sorry.
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter
Hmmm....I've just read one book about chromosome and it said that when forming a genetic pattern in the zygote (just take the male example), actually both genes in X and Y chromosome are in fight each other.
So, I can say that you inheritted that recessive X cromosome while that "fight" resulted a kind of thing that I can say as a "repairment" in that recessive gene in X chromosome...
That's only my opinion...
Q: Why are chemists great for solving problems?
A: They have all the solutions.
First of all, by definition, you are not technically considered color blind. The only people who are able to refer to themselves as being color blind are monochromats. These individuals have no functioning cones in their eyes and see everything in shades of lightness (white, grey, and black). Acer you have a color deficiency, called unilateral deuteranopia, which means that the cones in your left eye don’t see red and green properly. To answer your first question: Unilateral deuteranopia is always caused hereditarily by X-linked recessive genes.
To answer why your other eye is not expressing the trait, I need to explain normal vision. This will be a lengthy discussion, so bear with me. Normal sighted individuals (trichromats) see the world in three hues, which are blue, green, and red. There is monochromatic light, which is light of one wavelength, and natural light, which contains significant amounts of a large portion of the electromagnetic spectrum. Objects appear colored because they reflect light from particular regions of the visual spectrum and the light that is reflected is picked up by photoreceptors in your retina. Cone shaped receptors are only found in the fovea (cones deal with color vision, detail vision and vision in high levels of light), while the peripheral retina contains both rods and cones (rods are responsible for vision in low levels of light). The intensity of the light wavelength in relation to how much light is absorbed, determines what color you see. The color white reflects all the colors in the spectrum and the color black absorbs all the colors in the spectrum. This is why monochromats only see white, black and shades of grey, because they can only see one wavelength. The different wavelengths correspond to the cone shaped photoreceptors in your fovea. The size of the cone indicates the size of the photoreceptor response. The color blue corresponds to short length receptors, green to medium length receptors, and red to long length receptors. Dichromats experience some colors, but through a lesser range than trichromats. Deuteranopes like you, see blue at short wavelengths, yellow at long wavelengths, and have a neutral point (which is viewed as white) at about 498nm. Because you are missing the cones in your left eye that pickup medium wavelengths (green) and long wavelengths (red), this is why you see those colors as orange with your left eye. Deuteranopes can usually only distinguish between 2 or 3 hues, while someone with normal vision can see 7 different hues. Your case is very rare, because you only have this problem in one eye (unilateral) versus both eyes (bilateral). This makes you of special interest to researchers involved in color perception study…hint, hint… The reason your right eye is not expressing the same trait is because you have normal vision in the right eye (all three kinds of cone receptors are working fine). You only notice the deficiency when you close your right eye and look through your left (the eye where only two kinds of cone receptors are working). When you view things with both of your eyes at the same time, your eyes are cross-linked into your visual cortex, so your brain compensates for your left eye deficiency. Also, humans see trichromatically in their peripheral vision (remember, the peripheral vision contains both rods and cones). Since your eyes are constantly moving in saccades, there is a possibility that your peripheral vision is also helping you compensate.
I hope this helps!
Unilateral colour vision defects are most commonly associated with retinal pathology or compressive lesions involving the optic nerve/optic tract/occipital lobe of the brain. If the unilateral colour vision defect was detected using Ishihara plates only (ie a series of coloured dots which together form a number) then I would highly recommend you request (at the very least) a (computerised)visual field test or get another opinion.
In my limited experience, Ishihara plates were used to detect two cases of unilateral colour vision defects, the first of which was due to an extremely large pituitary macroadenoma and the second was due to normotensive glaucoma. Please note that colour vision assessment is not usually used to detect these diseases. Both had Humphrey visual field assessments, cranial MRI's (to detect intracranial mass) and OCT (like an MRI of the retina). If both of these tests were within normal limits, I guess the next step would have been FFA (fluorescein angiogram of the retina) and if ALL of these tests were within normal limits AND there was no progressive change to these tests over time, then you might consider the benign alternatives, such as congenital unilateral colour vision defect, however I would have written a journal article about it because it is soooo rare.
It is extremely rare to have a congenital unilateral colour vision defect and this should be treated as pathological until proven otherwise by a systematic battery of retinal and neurological tests.
In 303 mothers of colour-blind sons, both eyes were tested with pseudoisochromatic plates and with the anomaloscope. Two hundred thirty healthy normal and 56 colour-blind males served as controls. In good agreement with the expected proportion of homozygotes in our sample, 17 colour-blind mothers were detected. Eight others had difficulty reading pseudoisochromatic plates and were conspicuous at the anomaloscope. In these, both eyes were affected to a very similar, moderate degree. Monocular disturbances of colour vision were not observed in the entire series. Our data suggest that (1) in most (if not all) of the carriers with colour vision impairment, there is no complete lack of normal retina cones, and (2) the proportion of defective retina cones is remarkably similar in both eyes of individual heterozygotes.
The latter observation may indicate that at the time of X-differentiation there is a common primordial cell pool for both retinas.
I can say that you inheritted that recessive X cromosome while that "fight" resulted a kind of thing that I can say as a "repairment" in that recessive gene in X chromosome... ..
Last edited by honee_v on Fri Aug 19, 2011 6:06 am, edited 1 time in total.
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