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Lactase persistence or lactose tolerance is the continued activity of the lactase enzyme in adulthood, allowing the digestion of lactose in milk. In most mammals, ...
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]
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]
The majority of humans actually follow this protocol as well, and down-regulate lactase production around 3-5 years of age. Interestingly, though, the majority of caucasians, mainly those from northern european background, continue to have elevated lactase activity all the way into adulthood, and so they exhibit “lactase persistence”.
Analysis of his nuclear DNA indicates that he was a typical member of the Western European hunter-gatherer population at the time, with a most likely phenotype of blue-green eyes, dark brown or black hair, and dark or dark-to-black skin, with no genetic adaption for lactase persistence into adulthood. [4]
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.
Many adults are lactose intolerant because their bodies cease production of the enzyme lactase post childhood. 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 ...
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.