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Conservación de bienes culturales, de origen orgánico, procedentes de la Dirección de Salvamento Arqueológico – Coordinación Nacional de Conservación del Patrimonio Cultural

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Conservación de bienes culturales, de origen orgánico, procedentes de la Dirección de Salvamento Arqueológico – Coordinación Nacional de Conservación del Patrimonio Cultural
— Read on conservacion.inah.gob.mx/index.php/portfolio-items/co-conservacion-de-bienes-culturales-de-origen-organico-procedentes-de-la-direccion-de-salvamento-arqueologico/

MC1R Gene

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The MC1R gene provides instructions for making a protein called the melanocortin 1 receptor. This receptor plays an important role in normal pigmentation. The receptor is primarily located on the surface of melanocytes, which are specialized cells that produce a pigment called melanin. Melanin is the substance that gives skin, hair, and eyes their color. Melanin is also found in the light-sensitive tissue at the back of the eye (the retina), where it plays a role in normal vision.

Melanocytes make two forms of melanin, eumelanin and pheomelanin. The relative amounts of these two pigments help determine the color of a person’s hair and skin. People who produce mostly eumelanin tend to have brown or black hair and dark skin that tans easily. Eumelanin also protects skin from damage caused by ultraviolet (UV) radiation in sunlight. People who produce mostly pheomelanin tend to have red or blond hair, freckles, and light-colored skin that tans poorly. Because pheomelanin does not protect skin from UV radiation, people with more pheomelanin have an increased risk of skin damage caused by sun exposure.

The melanocortin 1 receptor controls which type of melanin is produced by melanocytes. When the receptor is activated, it triggers a series of chemical reactions inside melanocytes that stimulate these cells to make eumelanin. If the receptor is not activated or is blocked, melanocytes make pheomelanin instead of eumelanin.

Common variations (polymorphisms) in the MC1R gene are associated with normal differences in skin and hair color. Certain genetic variations are most common in people with red hair, fair skin, freckles, and an increased sensitivity to sun exposure. These MC1R polymorphisms reduce the ability of the melanocortin 1 receptor to stimulate eumelanin production, causing melanocytes to make mostly pheomelanin. Although MC1R is a key gene in normal human pigmentation, researchers believe that the effects of other genes also contribute to a person’s hair and skin coloring.

The melanocortin 1 receptor is also active in cells other than melanocytes, including cells involved in the body’s immune and inflammatory responses. The receptor’s function in these cells is unknown.

Melanisn

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MELANISM, meaning a mutation that results in completely dark skin, DOES NOT EXIST IN HUMANS.

Melanin is the primary determinant of the degree of skin pigmentation and protects the body from harmful ultraviolet radiation. The same ultraviolet radiation is essential for the synthesis of vitamin D in skin, so lighter colored skin – less melanin – is an adaptation related to the prehistoric movement of humans away from EQUATORIAL regions, as there is less exposure to sunlight at higher latitudes. People from parts of Africa, South Asia, Southeast Asia, and Australia have very dark skin, but this is NOT MELANISM.

The term MELANISM has been used on Usenet, internet forums and blogs to mean an African-American social movement holding that dark-skinned humans are the original people from which those of other skin color originate. The term MELANISM has been used in this context as early as the mid-1990s and was promoted by some Afrocentrists, such as Frances Cress Welsing.

“Melanin theory” is a claim in Afrocentrism that a higher level of melanin, the primary determinant of skin color in humans, is the cause of an intellectual and physical superiority of dark-skinned people and provides them with supernatural powers. It is considered a racist and pseudoscientific theory.

According to Bernard Ortiz De Montellano of Wayne State University, “The alleged properties of melanin, mostly unsupported, irrelevant, or distortions of the scientific literature, are (…) used to justify Afrocentric assertions. One of the most common is that humans evolved as blacks in Africa, and that whites are mutants (albinos, or melanin recessives)”. The melanin hypothesis was supported by Leonard Jeffries, who according to Time magazine, believes that “melanin, the dark skin pigment, gives blacks intellectual and physical superiority over whites”.

  1. Ortiz de Montellano, Bernard R. (17 Dec 2006). “Afrocentric Pseudoscience: The Miseducation of African Americans”. Annals of the New York Academy of Sciences. 775: 561–572. doi:10.1111/j.1749-6632.1996.tb23174.x. Archived from the original on 5 January 2013.
  2. Jaroff, Leon (4 April 1994), “Teaching Reverse Racism”, Time, vol. 143 no. 14, p. 74, retrieved 24 July 2016
  3. Tucker, S. D. (2016), “Science Fictions: Technological Utopia, Objectivity, and Other Scientific Myths”, Forgotten Science: Strange Ideas from the Scrapheap of History, Amberley Publishing Limited, ISBN 9781445648385
  4. Mehler, Barry (Fall 1993), “African American Racism in the Academic Community”, Retrieved from the Institute for the Study of Academic Racism (ISAR), Ferris State University. First published in The Review of Education, 15 (3/4), retrieved 12 August 2016
  5. Ferguson, Stephen C. (2015), Philosophy of African American Studies: Nothing Left of Blackness, Palgrave Macmillan, pp. 56, 66–67, ISBN 9781137549976
  6. Ortiz De Montellano, Bernard (Spring 1992), “Magic Melanin: Spreading Scientific Illiteracy Among Minorities”, Skeptical Inquirer
  7. Cashmore, Ernest; Jennings, James (2001), Racism: Essential Readings, SAGE, pp. 181–182, ISBN 9781446265482
  8. Morrow, Lance (24 June 2001), “Controversies: The Provocative Professor”, Time, vol. 138 no. 8, p. 19
  9. “Sundiata, AFROCENTRISM: THE ARGUMENT WE’RE REALLY HAVING”. Retrieved 2007-06-23