Hexachromy (Hexachromid)

Hexachromia (from the ancient Greek "hexa" - six and "chroma" - color) is the ability of a person to distinguish only six of the seven colors of the spectrum, with the exception of blue.

A healthy person has three types of cones in the retina, each of which perceives one of the three primary colors - red, green and blue. By combining signals from these cones, the brain can distinguish all colors of the visible spectrum.

With hexachromia, the cones responsible for the perception of blue color are absent or not fully functional. Because of this, a person cannot distinguish blue tones from blue and violet. For example, the blue sky or the azure sea may appear blue or even purple to them.

Hexachromia is a form of color blindness or color blindness. According to various estimates, it affects from 1% to 3% of men and 0.01% of women. This is a congenital disease caused by genetic mutations.

Despite limited color perception, people with hexachromia can function normally in everyday life. However, some professions that require fine discrimination of shades may be difficult for them.

Hexachromism occurs due to a genetic mutation when a person has only one or two alleles of the SWS1 gene, which code for red, green or yellow color vision pigment. About 40 carriers of this anomaly have been discovered, and despite the fact that it is inherited, the ability to distinguish all colors is not lost. A person with this type of perception differs from healthy people in the presence of a certain type of rods and cones in the eye. The most common symptoms are loss of the ability to recognize the color blue. They can be caused by low light or a cluster of electromagnetic waves in one region of the spectrum. Depending on

**Hexachrosia** is an unusual pupillary condition in which a person can only distinguish 6-7 of 12 colors. In the old days, several scientific copies were even broken about this rare disease! Scientists called the disease either color blindness or achromatopsia, but it received its correct name in 1997 thanks to Dennis Foggo and Mario Baumann-Mears from the University of Maastricht, who noticed that patients had pathology in 6 of 8 genes of the so-called melanocortin receptor (MC1R). The latter encodes a protein that regulates the synthesis of pigmentation-related substances such as melanin. By the way, eye color directly depends on it. Each of us has MC1R genes on 4 chromosomes - two from each parent. But their variations are only 2 genes and 3 alleles, 2 of which are normal genes, i.e. everyone either knows how to work correctly, or does not know how to do it at all, and represents a deviation from the norm. Each genetic mutation in the MC1R genes has its own insidious effect: * one causes a change in the color of all hair, * the other - only the skin, * the third - disrupts the production of melanin in both cases. The phenomenon of hexachromy was first described in 1772 by Jean Henri Mefferin and his friend Claude Patersen, who lived in France. “The siblings were extremely similar to each other,” Mefferen wrote. “They have absolutely the same facial features, figure and character. The only difference was that one of the brothers could distinguish completely seven colors and spoke seven languages, while the second could never distinguish yellow from brown.” Based on the above description of the nature of the mutants, scientists decided that the nature of their disease, that is, the altered genes, lies in a disruption of the mechanism of melanin synthesis. But a year later, the English doctor Sir William Gresham refuted this hypothesis, pointing out obvious clinical signs of an anomaly in the second of the mentioned brothers: he not only distinguished between yellow and brown