In 1794, John Dalton detailed his own colorblindness. He, like his brother, mistook crimson for green and pink for blue. In the research detailed here, DNA taken from Dalton's preserved eye tissue revealed that he was a deuteranope, lacking the retina's middlewave photopigment. His condition was not discovered until much later.
Dalton is now known as the father of modern chemistry because of his work on atomic theory. But he made another important discovery in his life: he was blind!
Blindness wasn't very common in England at the time, but it was still more common than today. Out of 100 people, about 7 would be blind. Of those 7, 2 were men: Dalton himself and his brother William. The only woman among the blind was Mary Anning, who was 11 years old when she lost her sight. She became one of the first women fossil collectors in Europe.
So blindness was not only common, but also likely responsible for many people being left out of society. This must have been very frustrating for Dalton, since he was such a talented scientist.
However, this didn't stop him from publishing several books during his lifetime. The first book he published at the age of 39 was On the Alkaline Water of Derby Valley, which studied the effects of acid rain.
Protan type color blindness causes a person to view greens, yellows, oranges, reds, and browns as more similar hues of color than usual, especially in low light. A typical issue is that purple hues appear more blue than purple. This means that someone with protan type color blindness will have a harder time distinguishing colors.
In general, people with color blindness struggle to distinguish some colors: red from green, yellow or white; blue from violet or brown. Because of this, they tend to under-use certain colors in paintings and advertisements, which can make these items less attractive aesthetically.
Color-blindness issues also cause problems for people when reading maps or other visual materials. For example, they may believe that the lines on a map are colors when they're actually directions or marks for orientation purposes.
Some people are born with color-blindness. It's estimated that about 1 in 10 men and 1 in 200 women are color blind. Color blindness is more common among males than females. People with color blindness experience difficulties distinguishing colors. They are usually able to recognize colors but need help differentiating between them. For example, a person who is color blind might describe red as blue or pink depending on how it is made up of other colors.
People with color blindness need not be resigned to a life without color.
The genes that cause red-green color blindness are inherited on the X chromosome. Red-green color blindness is more frequent in men since it is inherited on the X chromosome. This is due to boys inheriting only one X chromosome from their mother. Men have two copies of the X chromosome, one from each parent. Thus, men have three possible genetic combinations: both parents with color blindness (25% of color-blind people), one parent with color blindness and the other parent without it (50%), or neither parent with color blindness (25%). Women can pass on color-blindness genes without knowing it; this can happen if a woman has a mutation but is not genetically blind herself. Since women only have one X chromosome, they would receive the mutation on that single copy and would be color-blind too.
Color blindness is also associated with certain other physical traits and diseases. For example, people who are color blind are more likely to be blue-eyed than others. This is because people who are color blind tend to come from families where the parents are color blind too. If one parent is blue-eyed and the other brown-eyed, then their children will follow suit. Also, people who are color blind are more likely to have dark hair and eyes too.
The "gene" responsible for (inherited, red and green forms of) color blindness is exclusively located on the X chromosome. So, for a man to be colorblind, the colorblind "gene" just has to be present on his X chromosome. Color blindness must be present on both X chromosomes in a female. It cannot be caused by a genetic defect such as a mutation or an allele.
Color blindness is most often due to problems with distinguishing between certain colors, which affects all people who are color-blind to some degree. People who are color-blind may not be able to distinguish red from green, blue from yellow, or black from white. They may also have trouble distinguishing patterns that contain these colors simultaneously- for example, they may think there is a brown wall when there is actually one with orange and white stripes. Or they may think there is a gray car when there is actually one with pink upholstery.
People usually learn about their color vision as children when they are tested for eye health reasons. The color vision test looks at how well individuals can distinguish colors. If you pass, then you have normal color vision.
As adults, many people are still asked to identify colors accurately for purposes such as designing clothes, paintings, and posters. Those who fail this test may use it as a reason to purchase sunglasses that filter out specific wavelengths of light.
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