Genetic Traits Color Blindness

Most people take the ability to see a full range of colors for granted. We fail to keep in mind that some people are unable to see certain colors, such as red, blue, green and yellow; others are not be able to see any colors at all. Color blindness is usually an inherited trait, which means that if you are color blind, you have one of your parents has passed along this condition. Men are more likely than women to be color blind. An inability to distinguish red and green is the most common form of color blindness. While experts continue to research this disorder, there is currently no cure for color blindness.

About Color Blindness

People who are color blind have difficulty distinguishing certain colors from others. The most common form of color blindness is red-green color blindness, with blue-yellow blindness as the second most common form. Total color blindness is rare, and most people with color blindness can see at least some colors.

About 8 percent of men and less than 1 percent of women are color blind. Color blindness is generally an inherited trait, though it can have other causes, such as eye diseases and certain medications.

Biology of Color Blindness

In people with normal vision, light passes through the lens and the main body of the eye until it hits color-sensitive cones in the back of the eye. These cones contain chemicals that allow the eye to distinguish a wide variety of colors and then pass that information along to the brain. However, that are color blind, these chemicals are not present.

Genetics of Color Blindness

As previously mentioned, color blindness is an inherited trait. Mutations in several genes, including CNGA3, CNGB3, GNAT2, OPN1LW, OPN1MW, and OPN1SW lead to color blindness. The OPN1LW and OPN1MW genes cause red-green color blindness, whereas the OPN1SW gene causes blue-yellow color blindness. Mutations in the CNGA3, CNGB3, and GNAT2 lead to complete color blindness, also known as “achromatopsia.”

Red-green color-blindness, the most common form of this disorder, is an X-linked recessive trait. Men are much more susceptible to diseases caused by defects on the X chromosome. This is because men have only one X-chromosome. Because women have two X chromosomes, a mutation on one of the chromosomes can be mitigated by having a normal gene on the other chromosome.

About one in 10,000 people are blue-yellow color blind, and about one in 30,000 people cannot see any colors at all. Total color blindness is more common in areas where there are numerous marriages between relatives, and in the Pacific islands.

Interpreting Your Genetic Test Results

While genetic testing may be able to predict about 75 percent of all red-green color blindness, this testing is not currently commercially available. However, you may be able to guess your risk for color blindness, because the gene for most forms of color blindness is carried by the mother. If a woman carries the gene for color blindness, there is a 50 percent chance that her child will be colorblind.

Color blindness in children can usually be detected at a young age; signs include difficulty with color-coded games or learning exercises. Visiting an eye doctor is the best way to determine if your or your child is color blind. Tests performed by the doctor can determine the type and severity of your color blindness. A simple color blind test can also be done at home online.

Preventing and Treating Color Blindness

There is no cure for color blindness. However, color blind people may wear glasses with special lenses that help them distinguish certain colors. Color blind people may also learn to distinguish colors from each other through other cues. For example, people with color blindness may need to memorize the order in which colors appear in a stop light so they can correctly interpret the signal. If color blindness is inherited, its severity will not change over time.

Frequently Asked Questions about Color Blindness

Q: Who is most likely to be color blind?

A: Color blindness is most common in men of European descent. It is unusual for women to be color blind. About 10 million men in the United States suffer from red-green color blindness.

Q: Is there a cure for color blindness?

A: Currently, there is no cure for color blindness, though glasses with special lenses may help alleviate the problem for some people.

Q: Will the son of man who is color blind also be color blind?

A: Because women carry and pass on the genes for the most common forms of color blindness, the son of a color blind man will usually only develop the condition if he inherits the gene for color blindness from his mother.

Recent News on Color Blindness

In May of 2007, researchers at the University of Florida were able to restore vision in mice with achromastopia, or complete color blindness, using gene therapy. The research suggests that a similar therapy may someday be available for people with vision problems, including color blindness. Research on color blindness is not limited to the United States, however. Scientists in Australia determined in April of 2009 that certain types of sunglasses may make it even more difficult for color blind individuals to tell the difference between the colors of traffic signals.

Resources

American Association for Pediatric Ophthalmology and Strabismus (n.d.) Achromatopsia. Retrieved June 28, 2009, from the American Association for Pediatric Ophthalmology and Strabismus Web site: http://www.aapos.org/displaycommon.cfm?an=1