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Alle sondaars welkom: Gedagtes oor God en die grense van mense

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Jaco Strydom

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“Such then is the nature of quasispecies : the density of the sequence cloud at any point in sequence space is determined by the relative fitness of the sequence; regions of the cloud representing sequences of lesser fitness will be less densely populated and those with higher fitness, most populated. Here lies the most powerful quality of viral quasispecies: the density distribution of fitness variants dictates that sequences are represented at frequencies in relation to their relative fitness. Genomes with lower fitness will replicate poorly, or not at all, and the fittest genomes will replicate most efficiently. It therefore follows that there is a large bias toward the production of well-adapted genotypes: there are more of them, and they undergo most replicative cycles. This can permit viruses to experience evolutionary adaptation at rates that are orders of magnitude higher than those that could be achieved by truly random unbiased mutation. Sequences rapidly condense around the fittest area of the sequence space. Should the environment change, and, therefore, selective pressures change, a quasispecies can opportunistically exploits its inherent adaptive potential. Genotypes rapidly and ever-faster gravitate toward the cloud's new notational center of gravity. Changes in the fitness landscape of the sequence space that is occupied by a quasispecies are the natural consequence of altered selective pressures operating on the virus population. Such alterations may be the consequence of changed immunologic pressures exerted by the host, the application of antiviral drug therapy, or even cross-species transmission requiring the virus to adapt to a new host. Genotypes that once occupied the 'central' space, reserved for the fittest genotypes, are reduced in frequency and now occupy the more sparsely populated fringes of the fitness landscape; the very edge of the sequence cloud if you will. Here too lies an advantage for a quasispecies: it has a memory. The once best-adapted genotypes, now at a fitness disadvantage, can persist in the quasispecies as minor sequence variants. Under circumstances of fluctuating selective pressures, the ability of the population to recall an 'old' genome variant is a great asset. The quasispecies can rapidly respond and adapt by plucking out a preexisting variant and quickly coalescing around it to recreate an optimal fitness landscape.”

LandscapeFitnessGenomesFitness LandscapeQuasispecies
Book:Viruses: Agents of Evolutionary Invention
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“That is what the Slave Trade was all about. Not death from poxes and musketry and whippings and malnutrition and melancholy and suicide: death itself. For before the white men came to Guinea to strip-mine field hands. ... black people did not die ... the decedent ... took up residence in an afterworld that was in many ways indistinguishable from his former estate.”

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Book:The Chaneysville Incident
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“He turned into the road at that slow and ponderous gallop, the two of them, man and beast, leaning a little stiffly forward as though in some juggernautish simulation of terrific speed though the actual speed itself was absent, as if in that cold and implacable and undeviating conviction of both omnipotence and clairvoyance of which they both partook known destination and speed were not necessary.”

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“Everything started to move in slow motion. A vehicle was coming up the hill in the opposite direction, facing us but in its own lane. With vehicles parked on both sides of the road, this meant that there was just a narrow passage area for both vehicles to pass through. However, he had yet to reduce his speed, and now I knew which car he was going to hit. I was frozen stiff with fear in the front passenger seat, as I helplessly watched him slam into the back of a parked car. I was not wearing a seat belt, so upon impact my head crashed into the windshield. I was then slammed back into my seat, but with such force that everything went black.”

FearUnconsciousCar AccidentSlow MotionCar CrashSeat BeltsDrunk DrivingReckless DrivingBlack OutSensing Danger
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