Natural selection may shape human genome much more slowly than previously thought.Byline: ANI Washington, June 6 (ANI): A new research has indicated that natural selection may shape the human genome The human genome is the genome of Homo sapiens, which is composed of 24 distinct pairs of chromosomes (22 autosomal + X + Y) with a total of approximately 3 billion DNA base pairs containing an estimated 20,000–25,000 genes. much more slowly than previously thought. The research was conducted by a team from the Howard Hughes Medical Institute Howard Hughes Medical Institute, (HHMI), nonprofit medical research organization founded in 1953 by Howard Hughes and largly funded from proceeds of the 1984–85 sale of Hughes Aircraft. Headquartered in Chevy Chase, Md. , the University of Chicago, the University of California The University of California has a combined student body of more than 191,000 students, over 1,340,000 living alumni, and a combined systemwide and campus endowment of just over $7.3 billion (8th largest in the United States). and Stanford University Stanford University, at Stanford, Calif.; coeducational; chartered 1885, opened 1891 as Leland Stanford Junior Univ. (still the legal name). The original campus was designed by Frederick Law Olmsted. David Starr Jordan was its first president. . In recent years, geneticists This is a list of people who have made notable contributions to genetics. The growth and development of genetics represents the work of many people. This list of geneticists is therefore by no means complete. Contributors of great distinction to genetics are not yet on the list. have identified a handful of genes that have helped human populations adapt to new environments within just a few thousand years, which is a strikingly short timescale timescale Noun the period of time within which events occur or are due to occur timescale n → délais mpl timescale time (Brit) n in evolutionary terms. However, the team found that for most genes, it can take at least 50,000-100,000 years for natural selection to spread favorable traits through a human population. According to according to prep. 1. As stated or indicated by; on the authority of: according to historians. 2. In keeping with: according to instructions. 3. their analysis, gene variants tend to be distributed throughout the world in patterns that reflect ancient population movements and other aspects of population history. "We don't think that selection has been strong enough to completely fine-tune the adaptation of individual human populations to their local environments," said co-author Jonathan Pritchard. "In addition to selection, demographic history Demographic history may refer to:
To determine whether the frequency of a particular variant resulted from natural selection, Pritchard and his colleagues compared the distribution of variants in parts of the genome that affect the structure and regulation of proteins to the distribution of variants in parts of the genome that do not affect proteins. Since these neutral parts of the genome are less likely to be affected by natural selection, they reasoned that studying variants in these regions should reflect the demographic history of populations. The researchers found that many previously identified genetic signals of selection may have been created by historical and demographic factors rather than by selection. When the team compared closely related populations, they found few large genetic differences. If the individual populations' environments were exerting strong selective pressure, such differences should have been apparent. Selection may still be occurring in many regions of the genome, according to Pritchard. But if so, it is exerting a moderate effect on many genes that together influence a biological characteristic. "As functional studies go forward, people will start figuring out the phenotypes that are associated with selective signals," said lead author Graham Coop. "That will be very important, because then we can figure out what selection pressures underlie these episodes of natural selection," he added. (ANI) Copyright 2009 Asian News International The Asian News International (ANI) agency provides multimedia news to China and 50 bureaus in India. It covers virtually all of South Asia since its foundation and presently claims, on its official website, to be the leading South Asia-wide news agency. (ANI) - All Rights Reserved. Provided by Syndigate.info an Albawaba.com company |
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