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None of the mutations so far identified have been shown to be exclusively causal for lactase persistence, and it is possible that there are more alleles to be discovered. [39] If we focus on the "European variant", the position −13910 has an enhancer function on the lactase promoter (the promoter facilitates the transcription of the LCT gene).
However, mutations in the promoter region of the lactase gene (LCT) result in the continued production of lactase throughout adulthood in certain African populations, a condition known as lactase persistence. A study conducted by Sarah Tishkoff and her team shows that the mutation for lactase persistence has been under positive selection since ...
Both mutations, C→T at position -13910 and G→ A at position -22018, have been independently linked to lactase persistence. [27] The lactase promoter is 150 base pairs long and is located upstream of the site of transcription initiation. [27]
It is rarer in inland Southeast Asia and Southern Africa. While all Europeans with lactase persistence share a common ancestor for this ability, pockets of lactase persistence outside Europe are likely due to separate mutations. The European mutation, called the LP allele, is traced to modern-day Hungary, 7,500 years ago.
In most mammals, production of lactase diminishes after infants are weaned from maternal milk. However, 5% to 90% of the human population possess an advantageous autosomal mutation in which lactase production persists after infancy. The geographic distribution of lactase persistence is concordant with areas of high milk intake.
Lactase persistence in humans evolved relatively recently (in the last 10,000 years) among some populations. Around 8,000 years ago in modern-day Turkey, humans became reliant on newly-domesticated animals that could be milked; such as cows, sheep, and goats. This resulted in higher frequency of lactase persistence. [79]
Lactase persistence One of the best known examples is the prevalence of the genotype for adult lactose absorption in human populations, such as Northern Europeans and some African societies, with a long history of raising cattle for milk.
In 2004 he led a study to show that most lactase persistent Africans did not have the same mutation causing it as Europeans. [8] In 2007, in collaboration with Joachim Burger 's group in Mainz, Germany, he showed that the genetic variant that causes lactase persistence in most Europeans (-13,910*T) was rare or absent in early farmers from ...