Harvard University scientists say Darwinian evolution follows very few of the available mutational pathways to attain fitter proteins.
The study involved a gene whose mutant form increases bacterial resistance to a widely prescribed antibiotic by a factor of roughly 100,000.
The researchers' work indicates that of 120 five-step mutational paths that theoretically could grant antibiotic resistance, only about 10 actually endow bacteria with a meaningful evolutionary advantage.
"Just as there are many alternate routes one might follow in driving from Boston to New York, one intrinsic property of DNA is that very many distinct mutational paths link any two variants of a gene," said lead author Daniel Weinreich, a research associate in Harvard's department of organismic and evolutionary biology.
"Although this fact has been recognized for at least 35 years, its implications for evolution by natural selection have remained unexplored," Weinreich said. "Specifically, it is of great interest to determine whether natural selection regards these many mutational paths equivalently."
The research is detailed in the journal Science.
Copyright 2006 by United Press International
Related stories:
A more complex HIV family tree discovered
Adding another component into an already complicated effort to identify weaknesses within HIV, a team of Los Alamos scientists discovered that HIV variation in the human population is driven by more than a person’s immune response.
Tiny sacs released by brain tumor cells carry information that may guide treatment
Microvesicles – tiny membrane-covered sacs – released from glioblastoma cells contain molecules that may provide data that can guide treatment of the deadly brain tumor. In their report in the December 2008
Nature Cell Biology, which is receiving early online release, Massachusetts General Hospital (MGH) researchers describe finding tumor-associated RNA and proteins in membrane microvesicles called exosomes in blood samples from glioblastoma patients. Detailed analysis of exosome contents identified factors that could facilitate a tumor's growth through delivery of genetic information or proteins, or signify its vulnerability to particular medications.
Studies spot numerous undiscovered gene alterations in pancreatic and brain cancers
HHMI investigators have detected a multitude of broken, missing, and overactive genes in pancreatic and brain tumors, in the most detailed genetic survey yet of any human tumor. Some of these genetic changes were previously unknown and could provide new leads for improved diagnosis and therapy for these devastating cancers.
Natural selection may not produce the best organisms
"Survival of the fittest" is the catch phrase of evolution by natural selection. While natural selection favors the most fit organisms around, evolutionary biologists have long wondered whether this leads to the best possible organisms in the long run.
SEX4, starch and phosphorylation
Some of the new molecular mechanisms and regulatory components in starch metabolism have been identified by Dr. Samuel Zeeman and his colleagues. Dr. Zeeman, of the Institute of Plant Sciences, ETH Zurich, in Switzerland, who is the 2007 recipient of the Charles Albert Shull Award, will be presenting this work at the opening Awards Symposium of the annual meeting of the American Society of Plant Biologists in Mérida, Mexico (June 27, 2:30 PM). Mutational and structural analyses by Dr. Zeeman and his colleagues have revealed that starch degradation in Arabidopsis leaves at night differs significantly from the versions traditionally described in textbooks. Specifically, mutations at the Starch Excess 4 (SEX4), Maltose Excess 1 (MEX1) and other loci produce plants unable to metabolize starch to a usable form.
New research on mutation in yeast can enhance understanding of human diseases
Work from UNH Hubbard Center, Indiana University, others enhances understanding of genetics in human diseases
Yeast, a model organism heavily relied upon for studying basic biological processes as they relate to human health, mutates in a distinctly different pattern than other model organisms, a finding that brings researchers closer to understanding the role of evolutionary genetics in human diseases and cancer. The study, by researchers from the University of New Hampshire, Indiana University, Harvard University, and the University of Utah, appears in
Proceedings of the National Academy of Science (PNAS) Online Early Edition this week (June 16 – 20, 2008).
Researchers discover the dawn of animal vision
The findings are published in this week’s issue of the scientific journal PLoS ONE. The scientists studied the aquatic animal Hydra, a member of Cnidaria, which are animals that have existed for hundreds of millions of years. The authors are the first scientists to look at light-receptive genes in cnidarians, an ancient class of animals that includes corals, jellyfish, and sea anemones.
Beyond a 'speed limit' on mutations, species risk extinction
Harvard University scientists have identified a virtual "speed limit" on the rate of molecular evolution in organisms, and the magic number appears to be 6 mutations per genome per generation -- a level beyond which species run the strong risk of extinction as their genomes lose stability.