Langsung ke konten utama

human is one of Organisms at high altitude



Over 140 million people live permanently at high altitudes (>2,500 m) in North, Central and South America, East Africa, and Asia, and have flourished for millennia in the exceptionally high mountains, without any apparent complications. For normal human populations, a brief stay at these places can risk mountain sickness. For the native highlanders, there are no adverse effects to staying at high altitude.

 The physiological and genetic adaptations in native highlanders involve modification in the oxygen transport system of the blood, especially molecular changes in the structure and functions of hemoglobin, a protein for carrying oxygen in the body.[48][50] This is to compensate for the low oxygen environment. This adaptation is associated with developmental patterns such as high birth weight, increased lung volumes, increased breathing, and higher resting metabolism.


The genome of Tibetans provided the first clue to the molecular evolution of high-altitude adaptation in 2010. Genes such as EPAS1, PPARA and EGLN1 are found to have significant molecular changes among the Tibetans, and the genes are involved in hemoglobin production. These genes function in concert with transcription factors, hypoxia inducible factors (HIF), which in turn are central mediators of red blood cell production in response to oxygen metabolism.[54] Further, the Tibetans are enriched for genes in the disease class of human reproduction (such as genes from the DAZ, BPY2, CDY, and HLA-DQ and HLA-DR gene clusters) and biological process categories of response to DNA damage stimulus and DNA repair (such as RAD51, RAD52, and MRE11A), which are related to the adaptive traits of high infant birth weight and darker skin tone and, are most likely due to recent local adaptation.

 Among the Andeans, there are no significant associations between EPAS1 or EGLN1 and hemoglobin concentration, indicating variation in the pattern of molecular adaptation.[56] However, EGLN1 appears to be the principal signature of evolution, as it shows evidence of positive selection in both Tibetans and Andeans. The adaptive mechanism is different among the Ethiopian highlanders. Genomic analysis of two ethnic groups, Amhara and Oromo, revealed that gene variations associated with hemoglobin differences among Tibetans or other variants at the same gene location do not influence the adaptation in Ethiopians.[58] Instead, several other genes appear to be involved in Ethiopians, including CBARA1, VAV3, ARNT2 and THRB, which are known to play a role in HIF genetic functions.

 The EPAS1 mutation in the Tibetan population has been linked to Denisovan-related populations. The Tibetan haplotype is more similar to the Denisovan haplotype than any modern human haplotype. This mutation is seen at a high frequency in the Tibetan population, a low frequency in the Han population and is otherwise only seen in a sequenced Denisovan individual. This mutation must have been present before the Han and Tibetan populations diverged 2750 years ago.

 Source: https://en.wikipedia.org

Komentar

Posting Komentar

Postingan populer dari blog ini

Study suggests Mars hosted life-sustaining habitat for millions of years

In a new study announced on Monday and available in the current volume of Earth and Planetary Science Letters, an international team led by scientists from Brown University in the United States said the planet Mars once had the right water and temperatures to host simple life forms — just not on its surface. Mars's rocky, subterranean layer once, for some hundreds of millions of years, had enough water and reductants to support some of the same kinds of microbial communities seen on Earth. "We showed, based on basic physics and chemistry calculations, that the ancient Martian subsurface likely had enough dissolved hydrogen to power a global subsurface biosphere," reported lead author and current Brown graduate student Jesse Tarnas. The paper does not claim life on Mars did exist but rather that conditions suitable for life are very likely to have lasted for an extended time. This habitable zone, located beneath Mars's then-frozen surface, would have reached
1 komentar
Baca selengkapnya

Was a giant planet ejected from our solar system?

A fifth giant planet was kicked out of the early solar system, according to computer simulations by a US-based planetary scientist. The sacrifice of this gas giant paved the way for the stable configuration of planets seen today, says David Nesvorný, who believes that the expulsion prevented Jupiter from migrating inwards and scattering the Earth and its fellow inner planets. The Nice model (named after the city in France where it was devised) is currently the best explanation of why the solar system looks the way it does today. It describes how early gravitational interactions between the large outer planets and planetesimals – smaller bodies that are the building blocks of planets – would have scattered the latter throughout the solar system. This accounts for the period known as the “late heavy bombardment”, the scars of which bodies such as the Moon still bear today. It also helps explain the structure of the asteroid and Kuiper belts. However, for the model to work, the plane
Posting Komentar
Baca selengkapnya

Extraterrestrial life, Alien?

Extraterrestrial life,[n 1] also called alien life (or, if it is a sentient or relatively complex individual, an "extraterrestrial" or "alien"), is life that occurs outside of Earth and that probably did not originate from Earth. These hypothetical life forms may range from simple prokaryotes to beings with civilizations far more advanced than humanity.[1][2] The Drake equation speculates about the existence of intelligent life elsewhere in the universe. The science of extraterrestrial life in all its forms is known as exobiology. Since the mid-20th century, there has been an ongoing search for signs of extraterrestrial life. This encompasses a search for current and historic extraterrestrial life, and a narrower search for extraterrestrial intelligent life. Depending on the category of search, methods range from the analysis of telescope and specimen data[3] to radios used to detect and send communication signals. The concept of extraterrestrial life, and p
Posting Komentar
Baca selengkapnya