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The factors which affect the inheritance of color blindness will vary depending on whether a person is male or female and which parent has the defective gene which causes this condition. Men are more likely to be color blind than women, although it is a condition which is passed on to sons through their mothers. Some very rare forms of color blindness may have to be passed on by both parents, although this is not common.
Color blindness is a condition in which the affected person cannot recognize certain colors or mixes up some colors with others. The most common type is caused by a genetic defect found on the X chromosome and it is a condition which is almost always inherited. There are rarely certain conditions of the eye and drugs which may lead to color blindness.
Since most types of color blindness, called protanopia and deuteranopia, are carried on the X chromosome, men are more likely to have it because they only have one X chromosome paired with a Y chromosome. The X comes from the mother and the Y from the father, therefore, sons can only inherit color blindness from their mothers. If a woman has one parent who is color blind or who carries the gene, she will not have the condition because women have two X chromosomes and the normal one will override the defective one. Only two color blind individuals can produce a daughter who has the condition.
More rarely, the inheritance of color blindness may depend on both parents. Those who cannot see any color at all, rather than just having trouble distinguishing between certain colors, inherit the condition when both parents have the defective gene. This condition is extremely rare in both men and women, although men are still more likely to be born with this condition.
Another rare form of this condition is inherited equally as often amongst males and females. Hereditary tritanopia is a condition in which individuals cannot tell the difference between blues and yellows, whereas the most common form affects the defferientiation between reds and greens. The inheritance of color blindness which occurs in other rarer forms is usually decided in the same way as protanopia and deuteranopia, with the defective gene being passed on through the X chromosome.
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