How is Color Blindness Inherited?

By Parmu Malika

 

Introduction

Color blindness in most of the individuals is always an inherited trait. Since men have one X chromosome and women two, men are more prone to be color blind than women. Thus when a man inherits the gene for the defect he becomes color blind whereas a women when she inherits a single gene for the peculiarity will not be prone to the color vision defect. The reason is that the good X chromosome will control the defective gene inherited. Thus for a women to inherit the deficiency she must acquire the defective trait from both her parents.

The second cause for the defective color vision is through disease. Cataract is one of the most common causes for this inherited genetic deficiency. Also retinal and optic nerve maladies will also result in the deficiency. Medications like digitalis taken for heart disease, quinine for malaria and alcohol also ensue in color blindness.

Color blindness does not mean that the affected individual can see only black and white, but it means that they cannot see or they have trouble in making out the difference between some colors. Test yourself with the help of this diagram.


Cones and color Visualization

An individual's color vision is related to cones which are very small cells on the retina. The cones of 'red,' 'blue' and 'green' are susceptible to colors and combinations of them. All the three types of cones are required if the colors are to be perceived properly. If the combination of the cones is not correct then the brain is restrained from getting the exact message related to colors. A color blinded person will see a green color leaf as if it were tan or gray.


Forms of the genetic deficiency

Genetic color blindness is the result of hereditary disorders in the photoreceptor cells. The malfunctioning of different types of cone cells results in different forms of genetic color deficiency.

Difficulty in differentiating between the colors yellow, red and green is one type of the deficiency and difficulty in distinguishing between blue and yellow is yet another type of color blindness. The most uncommon type is mono chromic with the sufferer seeing only a black and white world.

The color blindness resulting in difficulty to distinguish red-green color is the most common kind of the genetic deficiency. This sort of deficiency affects about 2%-6% of all men. A person may also inherit this trait which reduces his/her capacity to distinguish between blue and yellow and the deficiency affects both men and women equally.

Hereditary color blindness can be inherited that is it can be present from birth, or it may start in childhood or adulthood. Hereditary color vision deficiency may remain the same all through a person's life. This depends on the mutation of the genes. It may also be progressive. Approximately 8% of males, and only 0.5% of females, are color blind in some way or another.

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