Year: 2022

CONFOUNDER. “The earlier potentiating mutations did not confer any immediate advantage with respect to using citrate, but they may have been beneficial with respect to growth on glucose. If so, it is possible that other populations in the LTEE have also become potentiated and might evolve the Cit+ phenotype, although no others have done so even after >50,000 generations.” https://www.nature.com/articles/nrg3564 View in LinkedIn

EXPERIMENTAL STRESS. “An important 'dial' that can be adjusted in experimental evolution studies is the strength of selection, particularly if the goal is to improve some phenotypic property. In one limit, selection may be so strong that it becomes a genetic screen in which only rare mutants with extreme, perhaps innovative, phenotypes can survive the stress (Fig. 2c).” https://www.nature.com/articles/nrg3564 View in LinkedIn

LESS STRESS. “When selection is less stringent, more genetic diversity can usually be sustained, which allows more opportunities for populations to optimize by exploring alternative mutational paths.” https://www.nature.com/articles/nrg3564 View in LinkedIn

MANY PATHWAYS. “Indeed, divergent paths have been described in most evolution experiments with microorganisms, and these dynamics have been reconstructed in certain cases.” https://www.nature.com/articles/nrg3564 View in LinkedIn

THE STRESS LEVER. “Stressful environments can sometimes help to separate the more beneficial mutations from the less beneficial mutations.” https://www.nature.com/articles/nrg3564 View in LinkedIn

TOOLBOX. “When there is genetic diversity in evolving populations for long periods of time, there is the opportunity for selection to operate not only on the immediate effects of mutations or new combinations of alleles but also on how those new genotypes differ in their capability to further evolve (that is, their evolvability).” https://www.nature.com/articles/nrg3564 View in LinkedIn

FITNESS LANDSCAPE. “In particular, prior mutational steps in a path on the fitness landscape may affect evolvability in at least two main ways. They may alter mutation rates (and/or recombination rates for organisms that are capable of sexual reproduction or horizontal gene transfer), or they may lead to differences in epistatic interactions with potential further mutations.” https://www.nature.com/articles/nrg3564 View in LinkedIn

HYPERMUTATORS. “It is fairly common for some populations in adaptive evolution experiments to become dominated by hypermutators that have increased mutation rates.” https://www.nature.com/articles/nrg3564 View in LinkedIn

BAD ACTORS? “How do hypermutators invade populations? The immediate effect of an increased mutation rate on fitness is invariably negative, on average, because more mutations are deleterious than beneficial (Box 1).” https://www.nature.com/articles/nrg3564 View in LinkedIn

SO ENDS this first of two weekends on the theme of mutations. Darwin’s theory of evolution depended on “descent with modification”, but at the time, nothing was known about genes or mutations. Today, mutations are exquisitely understood, but surprisingly rarer than expected, and even a single mutation can have an enormous phenotypic effect, causing diseases including Sickle-cell anemia, cancer, color blindness, Tay-Sachs disease, and neurofibromatosis. https://lnkd.in/dbDruwJm View in LinkedIn