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Color Blindness

Color Blindness 

 Color blindness or Color Vision Deficiency is a genetic disorder, more common in males than in females, due to mutations on one or more genes located in X chromosome. These genes code for proteins that absorb different wavelengths of visible light. These are visual pigments called photopsins, which are categorized as red, green or blue. A person with a normal color vision can distinguish different colors and their hues because they have all three categories of pigments in the retina. The absorption of different proportions of different wavelengths by the pigments is resolved by the brain as the color of the object. In human genes coding red and green pigments are located in X chromosomes and gene for blue pigment is on the chromosome 7. Since males have only one X chromosome and the relevant genes are absent in Y chromosome, any defect in one or both of these genes will make the phenotype. In females at heterozygous condition a defective allele in one X chromosome is masked by the good allele in the other. Therefore color vision deficiency is more common in males (5-8% of males) than in females (less than 1% of females). Color blindness nearly always affects the perception of red or green colors, because these are the genes that are sex linked.



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