GENETICISTS SOLVE 40 YEAR OLD DILEMMA TO EXPLAIN WHY DUPLICATE GENES REMAIN IN THE GENOME
Geneticists at Trinity College Dublin have made
a major breakthrough with important implications for understanding the
evolution of genomes in a variety of organisms.
They found a mechanism
sought for more than four decades that explains how gene duplication leads to
novel functions in individuals.
Gene duplication is a
biological phenomenon that leads to the sudden emergence of new genetic
material. 'Sister' genes -- the products of gene duplication -- can survive
across long evolutionary timescales, and allow organisms to tolerate otherwise
lethal mutations.
The Trinity
geneticists have now identified and described the mechanism underlying this
increased tolerance, which is known as 'mutational robustness'.
By experimentally
demonstrating that this robustness is important for yeast cells to adapt to
novel conditions, including those that are stressful to the cells, they have
underlined the likely reason for the existence of gene duplication.
"Natural
selection -- a process that keeps essential things in the cell -- also removes
genes that are redundant from the genome," said Dr Mario A Fares,
Assistant Professor in Genetics at Trinity, and leading author of the study.
"The mechanism
resolving the conflict between sister genes and their apparent evolutionary
instability had remained a mystery for decades, but we have now cracked this
latest part of the genetic code."
Gene duplication is a
frequent phenomenon in eukaryotic organisms (which safeguard their genetic
material within cell membranes), including yeast, plants, and animals. But
understanding how duplication leads to biological innovation is difficult
because evolution cannot be easily traced seeing as it occurs on timescales in
the order of millions of years.
Despite their
apparently redundant nature, duplicate genes that originated 100 million years
ago can still be found in today's organisms. This phenomenon has always
suggested the existence of a mechanism maintaining them in the genomes. The
researchers in this study chose to work with yeast -- an organism whose entire
genome has been duplicated over time -- to join up the dots.
They 'evolved' yeast
cells in the laboratory under conditions that allowed the spread of mutations
rejected by natural selection, by simply reducing the effect that natural
selection had on these 'maladapted' cells. They found that duplicate genes
tolerated the maladaptive mutations to a greater degree than non-duplicate
genes.
The geneticists'
simple experimental approach revealed that these genes, duplicated 100 million
years ago, were still able to respond to different environments as they
changed, as well as highlighting their potential to generate new adaptations
that might give them an advantage in new environments.
"Discovering the
mechanism of innovation through gene duplication marks an exciting beginning
for a new era of research in which evolution can be conducted in the laboratory
and theories hitherto speculative tested," added Dr Fares.
"Our discovery
also has implications for explaining the importance of redundancy in the human
society as well. The role of increased redundancies in a fashioned job market
in lenient economical conditions could lead, in crisis times, to the emergence
of new companies, specialized workforces, and the optimization of individual
capabilities, for example, although this requires a profound
investigation."
The research, recently
published online in the international journal, Genome Research, was
supported by Science Foundation Ireland (SFI).
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