[Paleopsych] UCSD Study Shows 'Junk' DNA Has Evolutionary Importance
checker at panix.com
Sun Nov 13 23:23:45 UTC 2005
UCSD Study Shows 'Junk' DNA Has Evolutionary Importance
October 19, 2005
By Kim McDonald
Genetic material derisively called "junk" DNA because it does not
contain the instructions for protein-coding genes and appears to have
little or no function is actually critically important to an
organism's evolutionary survival, according to a study conducted by a
biologist at UCSD.
In the October 20 issue of Nature, Peter Andolfatto, an assistant
professor of biology at UCSD, shows that these non-coding regions play
an important role in maintaining an organism's genetic integrity. In
his study of the genes from the fruit fly Drosophila melanogaster, he
discovered that these regions are strongly affected by natural
selection, the evolutionary process that preferentially leads to the
survival of organisms and genes best adapted to the environment.
Andolfatto's findings are important because the similarity of genome
sequences in fruit flies, worms and humans suggest that similar
processes are probably responsible for the differences between humans
and their close evolutionary relatives.
"Sequencing of the complete genome in humans, fruit flies, nematodes
and plants has revealed that the number of protein-coding genes is
much more similar among these species than expected," he says.
"Curiously, the largest differences between major species groups
appear to be the amount of `junk' DNA rather than the number of
Using a recently developed population genetic approach, Andolfatto
showed in his study that these expansive regions of "junk" DNA--which
in Drosophila accounts for about 80 percent of the fly's total
genome--are evolving more slowly than expected due to natural
selection pressures on the non-protein-coding DNA to remain the same
"This pattern most likely reflects resistance to the incorporation of
new mutations," he says. "In fact, 40 to 70 percent of new mutations
that arise in non-coding DNA fail to be incorporated by this species,
which suggests that these non-protein-coding regions are not `junk,'
but are somehow functionally important to the organism."
Andolfatto also found that "junk" regions exhibit an unusually large
amount of functional genetic divergence between different species of
Drosophila, further evidence that these regions are evolutionarily
important to organisms. This implies that, like evolutionary changes
to proteins, changes to these "junk" parts of the genome also play an
important role in the evolution of new species.
"Protein evolution has traditionally been emphasized as a key facet of
genome evolution and the evolution of new species," says Andolfatto.
"The degree of protein sequence similarity between humans and
chimpanzees, and other closely-related but morphologically distinct
taxa, has prompted several researchers to speculate that most adaptive
differences between taxa are due to changes in gene regulation and not
protein evolution. My results lend support to this view by
demonstrating that regulatory changes have been of great importance in
the evolution of new Drosophila species."
Comment: Peter Andolfatto (858) 334-8039
Media Contact: Kim McDonald (858) 534-7572
6. mailto:pandolfatto at ucsd.edu
7. mailto:kmcdonald at ucsd.edu
More information about the paleopsych