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The Jehoshua Novels


'Junk DNA' Defines Differences Between Humans and Chimps

Science Daily, October 25

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 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 lead 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 are reported in the most recent issue of the online, open-access journal Mobile DNA.

“These genetic gaps have primarily been caused by the activity of retroviral-like transposable element sequences,” said 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.”

3 comments to 'Junk DNA' Defines Differences Between Humans and Chimps

  • steeleweed

    there are three lines instead of two.

    In order of decreasing intelligence and ability:
      Humans.
      Chimps.
      Teabaggers, politicians, NeoCons, etc.

    BTW: Nice to see someone else follows ScienceDaily.


    “When you live on cash, you understand the limits of the world around which you navigate each day.
    Credit leads into a desert with invisible boundaries.”
    - Anton Chekhov

  • Raja

    A team of more than 60 researchers has decoded the DNA of a western lowland gorilla, which will help our understanding of human origins and may aid gorilla conservation efforts.

    Los Angeles Times, By Eryn Brown, March 8

    Scientists have decoded the DNA of the western lowland gorilla, a feat that could boost conservation efforts for the endangered apes as well as broaden researchers’ understanding of human origins.

    The complete sequence of 20,962 genes — extracted from the skin cells of Kamilah, a 34-year-old gorilla who lives at the San Diego Zoo Safari Park — was compiled by an international team of more than 60 researchers who worked on the project for about five years.

    “The gorilla genome is important because gorillas are our second-closest living relatives,” said Richard Durbin, senior author of a paper about the discovery published Wednesday in the journal Nature.

    By comparing the new gorilla DNA sequence with reference genomes of humans, chimpanzees, orangutans and macaques, scientists have already made a few surprising insights into the crucial periods when we diverged into separate species.

    For instance, the new genetic data bolster fossil evidence that gorillas split off as a separate species about 10 million years ago and that humans and chimps parted ways about 6 million years ago. Previous genetic evidence had seemed to point to a more recent split, prompting a contentious debate between genetics experts and fossil scholars, said Durbin, who leads the genome informatics group at the Wellcome Trust Sanger Institute in Hinxton, England.

    [...]

    The data also show that humans and gorillas differ in only 1.75% of their DNA, much less than previously believed. Humans and chimps, our closest living relatives, differ in only 1.37% of their genomes.

    When Durbin and his colleagues matched up the DNA letters of gorillas, chimps and humans, they found that in 15% of cases, gorilla DNA was more like human DNA than was chimp DNA.

    [...]

    One of the similarities is prompting scientists to reconsider how language developed in humans. Previous studies had shown that genes involved in hearing evolved rapidly in humans. But the new study found that auditory genes evolved rapidly in gorillas too — calling into question the interpretation that the genetic changes were linked to the rise of language.

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