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FAIL-SAFE DEVICES. “DNA replication involves a fail-safe system of error correction, with proofreading by the DNA polymerase backed up by a mismatch repair process that removes incorrect bases after the polymerase has moved on. A failure in either process still allows cells to make viable progeny, but simultaneous failure of both is lethal. In both biological and man-made systems, reducing the frequency of failure often requires an enormous increase in the complexity of circuits.” https://www.nature.com/articles/35011540 View in LinkedIn

MORE BIOLOGY DEVICES. “Coincidence detection lies at the heart of much of the control of gene transcription in eukaryotes, in which the promoters that regulate gene transcription must commonly be occupied by several different protein transcription factors before a messenger RNA can be produced.” https://www.nature.com/articles/35011540 View in LinkedIn

ENGINEERING IN BIOLOGY. “Designs such as these are common in biology. For example, one set of positive feedback loops drives cells rapidly into mitosis, and another makes the exit from mitosis a rapid and irreversible event. Negative feedback in bacterial chemotaxis allows the sensory system to detect subtle variations in an input signal whose absolute size can vary by several orders of magnitude.” https://www.nature.com/articles/35011540 View in LinkedIn

THE SELFISH GENE. “Survival of a gene pool, as opposed to an individual organism, is favoured by diversification, as the simultaneous presence of multiple phenotypes in a population increases the possibility that some individuals will survive and reproduce in a heterogeneous and changing environment.” https://www.nature.com/articles/35011540 View in LinkedIn

THE TWO EXTREMES. “Organisms have been selected for two properties: rapid reproduction in optimal conditions and the ability to survive rarely encountered extreme conditions. Because environments tend to fluctuate over time, most modules are likely to have been selected for their ability to contribute to both reproduction and survival.” https://www.nature.com/articles/35011540 View in LinkedIn

CRITICAL PLASTICITY. “Evolvability, on the other hand, requires that other parameters of modules are sensitive to genetic changes. They can then be modified over many generations to alter the function of a module, or its connections to other modules, in a way that allows organisms to adapt to new challenges. It is important to understand how robustness and flexibility can be reconciled for each functional module.” https://www.nature.com/articles/35011540 View in LinkedIn

CRITICAL ROBUSTNESS. “The survival of living systems implies that the critical parameters of essential modules, such as the accuracy of chromosome segregation or the periodicity of a circadian clock, are robust: they are insensitive to many environmental and genetic perturbations.” https://www.nature.com/articles/35011540 View in LinkedIn

UNTANGLING THE PRESENT BY THE PAST. “Today's organisms have an unbroken chain of ancestors stretching back to the origin of life. This constraint has been successfully used to understand protein functions, by comparing existing protein sequences from related species, finding conserved parts and inferring their roles. Comparing modules of common function from different organisms should be a similarly useful tool for understanding their operation.” https://www.nature.com/articles/35011540 View in LinkedIn

COMBINED RIGIDITY AND MESSINESS. “The principle arises from a combination of three mechanisms: exploration with selection (trial and error), error-correction mechanisms, and error-detection modules that delay subsequent events until a process has been successfully completed. These are present to different extents in different examples.” https://www.nature.com/articles/35011540 View in LinkedIn

TWO LEVELS OF SELECTION. “It is thus important to consider the function of modules not only in the context of an organism, but also from the point of view of the population of organisms, and to ask how modular construction facilitates the maintenance and selection of diversity.” https://www.nature.com/articles/35011540 View in LinkedIn