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Color Blindness Genetic disorders result from heritable abnormalities in the genetic makeup of a human. Disorders are often apparent at birth; however, others may develop during childhood or adult life. Some genetic disorders may result from a mutation in a single gene, which results in the absence or alteration of the protein that corresponds. Such an alteration disrupts some metabolic or developmental process, leading to a disease.
Color blindness is an example of a disorder that can be inherited if one copy of a defective gene is present. Color blindness is a defect in vision that causes problems in distinguishing between certain colors. It is caused by a defect in the retina or in other nerve portions of the eye. This condition is usually passed on genetically, and is more common in men than in women. Achromatopsia or monochromatism is color blindness in which all colors are perceived as different variations of gray.
This certain condition is congenital, extremely rare, and affects men and women equally. Partial color blindness, called dichromatism, is the inability to distinguish between reds and greens. However, the inability may be distinguishing between blues or yellows. Dichromatism is the most common form of color blindness, affecting about seven percent of men and less than one percent of women. (1) Dichromatism is identified as a sex-linked hereditary characteristic. This means it is a gene that occurs only on the X chromosome, which is passed to the child by the mother.
The Y chromosome that is passed to the child by the father, does not carry the defective gene. Therefore, children inherit color blindness only from their mothers. This makes men more likely to be color blind, since the gene for the trait is located on the X chromosome. Men have only one X chromosome, while women have two X chromosomes. If the man inherits the gene for a trait, he will have some kind of a color vision defect.
On the other hand, if a woman inherits a single gene for the trait she may not inherit a vision defect. This is because the woman s normal gene on her other X chromosome will dominate over the defective gene. A women will only be able to inherit color blindness if she inherits the defective trait from both of her parents. However, they may also result from diseases of the optic nerve or the optic cortex. People who are color blind often are not aware they have a vision problem until they are asked to distinguish between reds and greens or between blues and yellows. The vision of most color-blind people is normal in all other respects, and eventually most learn by experience to associate certain colors with varying sensations of brightness.
Some people who are colorblind have trouble distinguishing colors only when the light is dim, but are still capable of determining the difference between colors in good light. A less common type of color blindness makes it difficult for the person to distinguish between colors in any type of light setting Certain precautions must be taken by color blind people. For example, special attention must be given in determining traffic signals. Color blindness does not cause a great deal of hardship for an individual, but evidence has shown that they face a higher risk on the road. A German study found that men who were color blind were twice as likely to have rear-end collisions as were men who had normal vision. (2) About seven million North American drivers can not easily distinguish between the red and green lights.
Designers of traffic signals are working to make driving easier for these motorists. One improvement would be changing the shape of each of the different signals, so that color-deficient drivers can distinguish between stop and go. Another possible change would involve changing the color of brake lights. Improvements for driving may be made; however, individuals who are color blind may not be able to perform certain jobs. Many branches of the armed forces done recruit people who are color blind, and occupations such as airline piloting or fashion designing are not very practical. Several types of tests have been devised for a rapid diagnosis of color blindness and of the particular condition.
There are various pigment tests commonly used as diagnostic aids in the testing of color vision. The most widely used pigment tests are the pseudoischromatic plates, such as the Ishihara, Hardy-Rand-Ritter, Velhagen, and Dvorine plates. These tests show colored figures on a contrasting background in a pattern of dots. The objective for the person being tested is to distinguish the figure from its background. The people who are color blind will see different numbers or words than those who have a complete range of color vision.
A second type of pigment test involves the arrangement of a group of colored samples. The Farnsworth D- 15 Test and the Farnsworth-Munsell 100 Hue Test are examples of this type of test. In the United States, modern safety regulations require the tests for all transportation workers. In some states, color-vision tests are also given to drivers of private automobiles and to such public employees as police officers and firefighters. (3) Despite all of the technology today, there is no cure or treatment for color blindness. However, there is an abundant amount of research concerning the nature of vision in individuals with normal and limited color vision. With the increasing knowledge of vision, correction of color blindness may become a possibility in the future. 4 f 8 Color Blindness.
Microsoft (R) Encarta. 1994 Color Blindness. The Gale Encyclopedia of Science. 1996 ed. Color Blindness. Microsoft (R) Encarta. 1994 Bibliography Color Blindness, Microsoft (R) Encarta, 1994. Color Blindness, The Encyclopedia American International Edition, 1996 ed. , 7, 316 - 317. Color Blindness, The Gale Encyclopedia s of Science, 1996 ed. , 2, 876 - 877.
Genetic Diseases, Microsoft (R) Encarta, 1994.
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Research essay sample on Color Blindness Defective Gene
