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KNOCK-OUTS. “Later, parallel mutations in the adenine DNA glycosylase gene (mutY) arose in independent lineages; these mutations approximately halved the mutation rate, apparently by knocking out a mechanism by which misincorporations of oxidized nucleotides during DNA replication (caused by the original mutT defect) were misrepaired. The resulting reduction in genetic load was estimated to be ~0.5%.” https://www.nature.com/articles/nrg3564 View in LinkedIn

ALL IS CHANGE. “Solid land has been converted into sea. Sea has been changed into land. Marine shells lie far distant from the deep, and the anchor has been found on the summit of the hills.” (Page 13, Principles of Geology: Being an Attempt to Explain the Former Changes of the Earth's Surface, by Reference to Causes Now in Operation, Volume 1, By Sir Charles Lyell, Gérard Paul Deshayes). https://lnkd.in/dZDsbmvJ View in LinkedIn

HITCHHIKING MUTATIONS. “Indeed, both mutation-rate scenarios have been observed in an E. coli population in the LTEE. After thousands of generations, a mutation in the nucleoside triphosphate pyrophosphohydrolase gene (mutT) that caused a ~150-fold increase in mutation rates spread through the population, presumably by hitchhiking with one or more beneficial mutations.” https://www.nature.com/articles/nrg3564 View in LinkedIn

RISKY STRATEGY. “In the long term, increased mutation rates are not without evolutionary risk. Opportunities for mutations that greatly improve fitness will eventually run out in the optimization regime. It may then be beneficial to compensate for a hypermutator defect and to become less evolvable in order to lower the genetic load.” https://www.nature.com/articles/nrg3564 View in LinkedIn

POSITIVE IMPACT. “However, the hypermutator subpopulation has increased evolvability because it has a much higher per-capita chance of producing the next highly beneficial mutation, or multiple beneficial mutations, than a non-mutator competitor (Fig. 3a). Thus, despite their slight fitness costs, hypermutators can sometimes hitchhike to fixation with the beneficial mutations that they generate.” https://www.nature.com/articles/nrg3564 View in LinkedIn

FREQUENCY. “Given the balance between their high rate of occurrence and small fitness costs, hypermutators might exist at frequencies of 10(-6) -10(-4) in experimental populations of E. coli.” https://www.nature.com/articles/nrg3564 View in LinkedIn

ORIGIN. “However, the initial spontaneous mutation rate is typically low, as discussed above, so that the fitness cost of producing mutations at even a 100-fold higher rate is small. Furthermore, new hypermutator variants frequently arise because loss-of-function mutations in many genes give rise to this phenotype.” https://www.nature.com/articles/nrg3564 View in LinkedIn

FRAGMENT FROM NATURE continues from last weekend and ends this weekend on the theme of the very heart of evolution, inheritance with variation, or random gene mutation. The other face of evolution, natural selection, is performed by differential death and survival. Generate diversity, select and repeat. Generate diversity, select and repeat. This is evolution at its core. View in LinkedIn

Magnificent grove of plane trees in the Girona Devesa park. View in LinkedIn

MY EPITAPH. “Nothing perishes in this world; but things merely vary and change their form. To be born, means simply that a thing begins to be something different from what it was before; and dying, is ceasing to be the same thing. Yet although nothing retains long the same image, the sum of the whole remains constant.” (Ovid, Metamorphoses Book XV, 8 AD). https://lnkd.in/dhjhdUAs View in LinkedIn