For years, scientists believed the vast phenotypic differences between humans and chimpanzees would be easily explained – the two species must have significantly different genetic makeups. However, when their genomes were later sequenced, researchers were surprised to learn that the DNA sequences of human and chimpanzee genes are nearly identical. What then is responsible for the many morphological and behavioral differences between the two species? Researchers at the Georgia Institute of Technology (Georgia Tech) have now determined that the insertion and deletion of large pieces of DNA near genes are highly variable between humans and chimpanzees and may account for major differences between the two species. The research team led by Georgia Tech Professor of Biology John McDonald has verified that while the DNA sequence of genes between humans and chimpanzees is nearly identical, there are large genomic “gaps” in areas adjacent to genes that can affect the extent to which genes are “turned on” and “turned off.” The research shows that these genomic “gaps” between the two species are predominantly due to the insertion or deletion (INDEL) of viral-like sequences called retrotransposons that are known to comprise about half of the genomes of both species. The findings were published October 25, 2011, in the online, open-access journal Mobile DNA. “These genetic gaps have primarily been caused by the activity of retroviral-like transposable element sequences,” said Dr. McDonald. “Transposable elements were once considered ‘junk DNA’ with little or no function. Now it appears that they may be one of the major reasons why we are so different from chimpanzees.” Dr.
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