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Washington (pte033/20.06.2005/13:40) - By doing extensive and complicated tests with DNA, scientists at the University of Washington in Seattle, US, have found that humans may have evolved through rapid bursts of genetic change, rather than by gradual evolution.
By studying human chromosome 2, the researchers discovered that the bulk of its DNA changes occurred in a relatively short period of time and that only minor alterations have occurred since then. This highlights a theory called 'punctuated equilibrium', which suggests that evolution actually occurred as a series of jumps with long static periods between it.
Associate professor of genomic sciences at the University of Washington in Seattle, US http://eichlerlab.gs.washington.edu , Evan Eichler and colleagues looked at duplicated DNA sequences on a specific section of chromosome 2, and compared them with ape genomes and Old World monkey genomes. Rather than finding that duplications had occurred gradually over the last few million years, they found that the large duplications had occurred in a relatively short period of time, after which only smaller rearrangements occurred.
The main duplications were present in the genomes of humans, chimpanzees, gorillas and orang-utans, but were absent in Old World monkeys - such as baboons and macaques.
Laurence Hurst, professor of evolutionary biology at the University of Bath in the UK http://www.bath.ac.uk/bio-sci/hurst.htm , says that although the study was interesting, the 'punctuated evolution' theory needed to be demonstrated for other chromosomes, to give the general pattern more assurance. "There is growing evidence that evolutionary processes may occur in bursts," Hurst said. "We now know, for example, that 50 million years ago there was a burst of activity that resulted in lots of new genes being produced,"
Work on chromosomes will continue in order to try and find out how they correlate with changes in gene function or expression.
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