The dark skin of Ashkenazi Jews has always been a controversial topic in Spain.
As a group, the dark-skinned Jews of Spain have long been persecuted and forced to wear distinctive black robes to preserve their dark complexion.
But now, the Spaniards are being asked to explain their dark skin.
What they have to say is in stark contrast to the stereotype that they are pale-skinned and thin.
Spanish scientists have found that a genetic mutation known as Ashkenazic-Caucasian variation (ACS) in the gene encoding the enzyme melanocortin receptor (MC1R), which controls melanin production, may play a role in how Ashkenas dark skin develops.
According to a new study, the mutations are responsible for a genetic difference that occurs when Ashkenos dark skin is produced in the womb.
“The new research reveals that the recessive mutation in MC1R may cause darker skin development in early life,” study author Jose Maria Cordero, a geneticist at the Instituto Nacional de Estudios Energética y Neurosciences in Madrid, told Reuters Health.
“This results in a genetic alteration that appears in the first weeks of life, and is associated with a different phenotype.”
The study, published online March 16 in the journal Science, also reveals that a similar mutation also appears to play a part in skin color development.
“Although the genetic variation responsible for the dark skin color is still unknown, the fact that we have discovered a similar effect in human embryos suggests that this gene mutation may also influence the development of dark skin in early development,” Corderos co-author Sergio Martínez, also from the Institut de Recherche Scientifique de Madrid, said in a statement.
The genetic study is one of several that have been conducted over the past several years to understand how different recessive mutations cause dark skin and how they may contribute to skin color.
The findings could help researchers understand the genetics of other genetic disorders that may affect the appearance of dark-skinned people, such as Down syndrome.
Previous studies have found recessive MC1r mutations in about 1 percent of the general population and in about 20 percent of European Americans.
A large percentage of Ashkeins in Spain have dark skin because of a mutation known locally as “Caucasus mutation,” which occurs in the same region of Europe as the one causing dark skin, said the study’s lead author, Cristina Fernandez, an assistant professor of genetics at the University of Bordeaux.
But Fernandez and her colleagues found that the mutation that causes dark skin has been detected in a small number of Ashkings and some other people with darker skin, but not in a large proportion of European Ashkenais.
In the study, Fernandez and other researchers looked at the genes that control MC1Rs, or melanocorins, in skin cells.
The gene’s structure is similar to that of the MC1 gene, which is the gene that regulates how the enzyme works.
The enzyme converts light to dark pigment and converts it into melanin, which helps skin produce melanin-producing melanocytes, or skin cells that produce melanins.
However, because Ashkenians share more than one MC1 r gene, the Ashkenazes of Spain were more likely to inherit a mutation that caused the Ashkeas dark-colored skin, the researchers found.
The mutation appears to be inherited in about one percent of Ashknights in Spain and in 10 percent of other Ashkenes in Europe.
The researchers also found that in about 10 percent, a recessive variant of the mutation causes a very dark-looking skin tone.
This mutation occurs more often in Ashkenese people with lighter skin than in Europeans.
The recessive variants of MC1 are also associated with lighter pigmentation in the skin of certain African-Americans and other dark-complexioned people.
In a separate study, a team of researchers from the University and University of Southern California examined more than 100,000 people with Ashkenasy or other skin pigmentation disorders.
In all, they looked at people who had one or more MC1 rs variants, as well as the people with a milder MC1 variant, to see if there was a genetic link between these disorders.
They found that Ashkenites with lighter melanin pigmentation have higher odds of being Ashkenafic (white skin color) or Ashkenawid (dark skin) than Ashkenath (dark-skinned people).
In addition, the study found that more than half of the Ashkners had the mutation, which occurs after the third trimester of gestation.
In other words, the mutation was present in people from the first trimester, but did not occur until after birth.
“In other words,” the researchers wrote in the paper, “the Ashkenase phenotype is inherited before birth.”
The findings are