Evolution: Computer simulations of mutations (Introduction)

by David Turell , Monday, June 08, 2015, 22:18 (3238 days ago) @ Balance_Maintained

The study makes a series of assumptions about mutations, ignoring epigenetics, so their assumptions influence their results. Of course evolution is a contingent series of unpredictable events:-"The study focuses exclusively on the type of evolution known as purifying selection, which favors mutations that have no or only a small effect in a fixed environment. This is in contrast to adaptation, in which mutations are selected if they increase an organism's fitness in a new environment. Purifying selection is by far the more common type of selection.-"'It's the simplest, most boring type of evolution you can imagine," Plotkin said. "Purifying selection is just asking an organism to do what it's doing and keep doing it well."-"As an evolutionary model, the Penn team used the bacterial protein argT, for which the three-dimensional structure is known. Its small size means that the researchers could reliably predict how a given genetic mutation would affect the protein's stability.-"Using a computational model, they simulated the protein evolving during the equivalent of roughly 10 million years by randomly introducing mutations, accepting them if they did not significantly affect the protein's stability and rejecting them if they did. They then examined pairs of mutations, asking whether the later mutation would have been accepted had the earlier mutation not have been made. -***-"An implication of these findings is that predicting the course of evolution, as one might wish to do, say, to make an educated guess as to what flu strain might arise in a given year, is not easy.-"'The way these substitutions occur, since they're highly contingent on what happened before, makes predictions of long-term evolution extremely difficult," Plotkin said.-"The researchers hope to partner with other groups in the future to conduct laboratory experiments with microbes to confirm that real-world evolution supports their findings.-"And while Gould's comment about replaying the tape of life was mainly a nod to the large amount of randomness inherent in evolution's path, this study suggests a more nuanced reason that the playback would appear different.-"'There is intrinsically a huge amount of contingency in evolution," Plotkin said. "Whatever mutations happen to come first set the stage for what other later mutations are permissible. Indeed, history channels evolution down a certain path. Gould's famous tape of life would be very different if replayed, even more different than Gould might have imagined.'"-
 Read more at: http://phys.org/news/2015-06-evolution-unpredictable-irreversible-biologists.html#jCp